Real Street Performance

No appologies necessary. I'm not upset, other than maybe that my post has been hopelessly hijacked. :rolleyes:

Anyway, the other day I was just looking at the dyno charts for the two cars (back to post #1) and it occurred to me that the gains looked very similar but different on the two examples of overdriving different blowers. That is what started this post. I had hoped it wouldn't end up this way. :eek:
 
CMac89 said:
All we need is a dyno chart of the AR to compare it to the MPIII. That will tell you the whole story. If the tq and hp curves look the same on an AR as the MPIII, but higher numbers, then end of story.

In any experience with drag racing, running a car off of torque is a joke. HP will ALWAYS be greater of an advantage than torque is. There's plenty of examples. I can't set the converter in my race car at peak torque because it won't fall out of a tree and becomes 5-7 tenths slower. Why do Pro stockers make 1400HP and 800lbtq and still run 6.60's? Not because of torque....

Case and point, the more power you can make at a higher rpm the faster/quicker your car will be.

This is exactly what one of my all time hero's once said. "You race HP, but you drive torque."

For racing, a higher peak HP number is better, as is a high average HP number. However, on the street torque is king. It's what you feel when you mash the throttle. HP can be deceiving but torque is very noticable and fun to drive.

This is the point that Paul was making earlier and people often have a hard time accepting. If you build a street motor with an emphasis on HP you will often lose in the stoplight battles and while the car will be fun when you get the chance to really open it up, you will get embarrassed more often than not in most impromptu situations.

On the other hand a motor built for torque will always bring a smile to your face and will surprise a lot of people in quick encounters. Of course it will lose in a long head to head run but then you've crossed the line into "Racing HP" vs. "Driving torque."
 
CMac89 said:
All we need is a dyno chart of the AR to compare it to the MPIII. That will tell you the whole story. If the tq and hp curves look the same on an AR as the MPIII, but higher numbers, then end of story.

In any experience with drag racing, running a car off of torque is a joke. HP will ALWAYS be greater of an advantage than torque is. There's plenty of examples. I can't set the converter in my race car at peak torque because it won't fall out of a tree and becomes 5-7 tenths slower. Why do Pro stockers make 1400HP and 800lbtq and still run 6.60's? Not because of torque....

Case and point, the more power you can make at a higher rpm the faster/quicker your car will be.
explain 8000 pound diesel trucks running 11's big blocks offer low rpm torque, small blocks offer high rpm hp, so why would anybody run big blocks? and dyno's measure torque and h/p is a mathmatical equation off of the torque. that is why at 5200rpm torque and hp will allways cross
 
I never thought that I'd live to see the day when the Sc community actually had to have a technical discussion over which parts from which vendors were best. OMFG


<----- clutching chest and gasping for air...doing my best Red Fox imitation
I think this is the big one!! I m comin for you Elizabeth, I'm coming...

I remember when the only mods available were the Maf and Blower pulley. Charles and Dave have both provided a great service in terms of furthering the development of the Sc as a viable platform for all types of driving enjoyment.

I, for one, are very interested to see where this thread leads. My blower choices very well may depend on it.

Rick
 
CMac89 said:
All we need is a dyno chart of the AR to compare it to the MPIII. That will tell you the whole story. If the tq and hp curves look the same on an AR as the MPIII, but higher numbers, then end of story.

That would be no fun at all. I'd rather "duke it out" on the track. :D

But in all fairness, the torque and hp curves will not look the same at all. ;) Also, it would not be fair to embark upon such a test until such time as both parties have had the chance to optimize the performance of each unit.
 
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XR7 Dave said:
That would be no fun at all. I'd rather "duke it out" on the track. :D

But in all fairness, the torque and hp curves will not look the same at all. ;) Also, it would not be fair to embark upon such a test until such time as both parties have had the chance to optimize the performance of each unit.

HEHE! Sounds like a challenge!:D
 
Kevin Leitem said:
explain 8000 pound diesel trucks running 11's big blocks offer low rpm torque, small blocks offer high rpm hp, so why would anybody run big blocks? and dyno's measure torque and h/p is a mathmatical equation off of the torque. that is why at 5200rpm torque and hp will allways cross
I can assure you that if the diesels could switch HP and torque it would run faster than that.

I can assure you that if Pro stock switched HP and Torque it would be atleast 2 seconds slower.

I can assure you that if on your own car you switched torque and HP numbers then it would run 10's with a high 1.6 60ft.

I can assure you that if I made 388rwhp and 270rwtq instead of 270rwhp and 388rwtq then my car would have run 12's.

My point being that most of the power and time an engine spends is in the mid-high rpm's. The more power you can make up to in a single gear the faster/quicker it would be. If you like torque then go tree stump pulling and don't go to the race track (a comment in general, not pointed at you).
 
Case and point, the more power you can make at a higher rpm the faster/quicker your car will be.

If your car is set up to take advantage of that RPM through gearing then yes you can go faster. There is so much more then just peak numbers responsable for going fast though. And in the end all that matters is who crosses the finish line first.
 
DamonSlowpokeBaumann said:
If your car is set up to take advantage of that RPM through gearing then yes you can go faster. There is so much more then just peak numbers responsable for going fast though. And in the end all that matters is who crosses the finish line first.

That was my mistake and one of the reasons that I never got to post a decent time last year. Crossing the finish line at 4800rpm will do that to you. :(
 
All i'm really trying to say is that if you want more torque then gear it. You can manipulate your torque by gear multiplication to the road, but a dyno won't show it.

If you have a car that only makes 200lbstq then put a 6.00 gear in it and it now has 1200lbstq (not counting tranny gears)

You can easily produce torque through gear multiplication, but with HP it's all about right engine parts working together.
 
Eaton had many requirements when developing the M90 that included noise emissions as Ford must pass federal limits on noise as well as pollution, gas mileage, etc. To reduce noise Eaton designed rather small intake and exit ports and added the noise reduction vents. Aftermarket companies do not have to meet these additional requirements so MP was able to give up noise reduction in favor of performance. As a result the later blower ports have more of the classical Roots whine.

Small blower ports do not reduce blower efficiency when the supercharger is turning slowly as the rotor cavities have plenty of time to fill with air however as RPM increases the volumetric efficiency (VE) decreases causing the supercharger to not move the amount of air expected because of air flow restrictions. Reduced VE also causes the supercharger discharge air temperature to increase dramatically because there is more resistance to air movement. For instance early this season Kevin ran an “S” model with 15% overdrive, the best time he could make with it this season was 11.8. After returning to the pits he would ice down the blower, when he put the ice on the blower’s case the ice would sizzle as the case temperature was well over the boiling point. Now with the MPIII when he returns to the pits he can put his hand on the blower without getting burnt running 25% OD. That means the MPIII is much more efficient when running 15% or greater overdrive compared to the “S” model and less power is turned to waist heat. As most people on this BB knows Kevin has run repeated 11.3x with the MPIII. That is a full .5 seconds faster then what he did with the “S” port.

The Belt Slip Issue:
Several factors are involved including coefficient of friction, pressure between the belt and pulley, surface area, belt tension, torque, RPM and centrifugal force.

Smaller pulley diameter reduces surface area and in addition they increase the “pull” the belt must exert to turn the supercharger at any particular torque valve. Lets say for example the supercharger takes 10 ft pounds to turn. That means if the supercharger pulley had a 12-inch radius the belt would see a 12-inch moment arm so a force of 10 pounds would turn the supercharger. Now let us take for example a pulley that has a 1.2” radius (2.4” diameter) the same 10-pound torque valve would place a strain of 100 pounds on the belt. So in order for the belt to turn the pulley without slipping it would require 10x the traction required compared to the first example. Now these are extreme examples (12” and 1.2” radius) but makes the point clearly, small diameter pulleys create a situation that enhances the possibility of belt slippage from reduced surface area and increase belt strain because of reduced leverage.

Increased RPM increases centrifugal that tries to force the belt away from the pulley surface decreasing the pressure between the belt and the pulley thereby reducing traction. Centrifugal force increases with the square of RPM so it can be seen this parameter increases rapidly as RPM increases. There are two terms that come into effect when considering centrifugal force, one is the weight of the belt and the other is the strength of the tensioner whose function it is to force the belt against the pulley surface. For instance if you install a wider belt say 8 ribs to replace a 7 rib belt you increase the belts weight and in doing so increase the force trying to move the belt away from the pulley. Increasing the width of the belt increases the surface area but if that surface area is not forced against the pulley it will all be for not.

The Super Coupe’s tensioners are very weak and apply little pressure compared to other similar cars and trucks that use Eaton superchargers. I measured the top tensioner at 12ftpds torque required to turn the tensioner arm and the bottom tensioner can be turned with only 7ftpds. By comparison the 04 Cobra and Lightning tensioners require between 45 and 50ftpds. It can be seen the SC tensioners are much weaker and are contributing significantly to the belt slip issue.

So far Kevin has the simplest and least expensive method to increase the force the tensioner applies to the belt. He welded two bolts together head to head and screwed one end into the hole the keeps the idler pulley in place and to the other end attached a spring that was connected to the block with a turnbuckle in between. He made two; one for the lower and one for the upper, parts for both were purchases from a hardware store for $10 and he has had good results up to 25% OD.

Higher boost pressure increases the torque required to turn the supercharger. Superchargers have something called “Swept Area” that determines the displacement of the supercharger. Divide swept area by the distance traveled when turned and you get the effective surface area of the rotors. Boost pressure impinges on the rotor’s surface area and generates a force (torque) that must be overcome to turn the supercharger. The torque goes up as boost pressure goes up and is independent of the supercharger’s antibiotic efficiency. I should point out here that if the belt is slipping or on the verge of slipping with a “S” model or MPII and the MPIII is installed it may not make more power because of its increased VE, let me explain. At high RPM the MPIII will move more air then the “S” or MPII causing the boost pressure to increase. Increased boost pressure will increase the torque required to turn the supercharger. If the pulley system is at its limit of traction it can not apply the required torque so the belt begins to slip more and boost pressure will not increase so more power is not developed but additional power will be converted to heat by heating up the pulleys because the belt is slipping. I am sure you can see it is critical the belts are not slipping.

We can see there is several parameters that come into play that cause belt slippage. At this point is seems weak tensioners are a major contributor and is something that is easily remedied. Larger pulley diameters instead of smaller ones to increase blower OD is also of benefit.

Real World Results:
The MPIII was tested at Fast Specialties on two SC’s one had a stock engine and the other had ported heads and a mild cam. Both SC’s were in good running condition, were properly tuned and the drive belts were not slipping. The built engine had all MP add-ons including FMIC, 85mm TB, Raised Top and Cold Air Intake. Running 15% overdrive the MPII made 345 rwhp on pump gas. When the MPIII was added with no other changes power went to 375rwhp and 440 rwtq an increase of 30hp. Power at the beginning of the pull were about the same for both superchargers but as RPM increased the MPIII began to out pass the MPII making the 30hp gain at 5,000 rpm. The OD was then increased to 20% and power increased to 390rwhp and torque increased to 469rwtq an additional 15hp making a total 45hp increase at that point. The additional 15hp was present all the way through the pull, i.e., 15hp at 2,500 rpm and 15hp at 5,000 rpm. The stock engine SC made 318rwhp with the MPIII at 15% overdrive with a 70mm TB and stock IC. I do not have data on this engine with the MPII or other superchargers here; perhaps I can get it from Fast Specialties at a later date.

It has been shown the MPIII on the dyno is capable of making significant HP improvements over the MPII if everything is in order. Kevin’s track results confirm the MPIII is making good power compared to the “S” port as he has cut .5 seconds off his ¼ mile time by running the MPIII. A track HP calculator suggests he is making 417 hp to be running those times at his weight.

In summery it is clear the MPIII allows the supercharger to be spun faster to force more CFM into the engine creating more power as compared to the ”S” model and the MPII. It has also been show the MPIII can make 30rwhp more power over a MPIII running 15% overdrive. More RPM increases centrifugal force and more boost pressure increases the torque required to turn the supercharger both of which increases the chances of belt slippage. Helper springs to increase belt tension has been shown to work well up to 25% overdrive and they can be made for about $10. Kevin’s experience has shown the MPIII runs cooler then his “S” model did while also making more power. And Kevin has shown the MPIII can be ran at those boost levels with Race fuel or on the street running pump gas.


Charles
 
I generally get lower torque readings on the dyno with a lower gear. Converters also come into play. I have seen some cars put down some awful dyno #'s that have had crazy rear gears and high stall converters yet run amuck at the track.

Torque and HP go hand in hand

For those that really dont understand the HP torque concept here is a decent writeup which saves me the time of explaining it. We can rip into this subject after this read. May be from a GM guy but hey....

http://vettenet.org/torquehp.html
 
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A lot of Buick GS Stage 1 cars embarrassed quite a few cars at the track. The factory ratings were 360 horsepower and 510 ft-lb torque. Now, the horsepower rating was probably under estimated but all that torque made the car get up and go.
 
HP Versus Torque

Well the truth of the situation is it is AVERAGE HP that accelerates you down both track and street. On the track it’s the average hp from the starting line to the finish line that is BTW always exactly ¼ mile from the starting line that wins. Street racing is much less defined and can be anything two people decide to do most of which includes breaking the law. It could be anything from one red light to the next acceleration race or blasts down the interstate to 175mph. In any case it is the average hp over that time interval that will win.

Kevin has pointed out HP= Torque X RPM / 5200. Torque does nothing if there is no movement, i.e., for instance 2,000 pounds torque time zero RPM divided by 5200 equals Zero. So Torque does nothing without RPM therefore torque is not what gets you going or any such thing. Since Maximum torque tends to occur at a low RPM the term “Torque” has been adopted as a “Short Hand” for low RPM HP.

I have attached a dyno chart of MP’s blower for the F150 Lightning. The chart shows the power produced when overdriven at two different OD ratios. The blower had a 2.7” diameter pulley and the crank pulleys were 9 5/8” and 10 ¾” meaning the blower was being overdriven about 4 to 1. With the smaller pulley the engine made 516 peak hp as compared to the pull with the large pulley that made 523, just about the same for all practical purposes however the small pulley made 554ftpds torque while the large pulley made 647ftpds torque nearly 100 ft pounds more torque. Now look at the HP chart and see the difference in HP between the two pulley setups. Down low the engine with the big pulley was making nearly 75 more hp and throughout most of the pull it was making between 30 hp to 50 hp more then the pull with the small pulley.

Now I know that is a Lightning and not a Super Coupe but it is nonetheless an example of two different dyno pulls with similar peak HP numbers but one had a higher torque number and much higher average hp. It is clear no matter if you are going stop light to stop light or down the ¼ mile the engine with greater average hp will win and that will be the one with the greater torque number as in this example.

Charles
 

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Of course comparing dyno numbers will only get you so far, and I suppose in many cases do nothing but get you into trouble, but nonetheless I have a question.

Please follow my logic here.

My car has been dyno'd many times over the years. I have kept the dyno charts and notes of what mods the car had at each dyno session. I have done this for my own purposes only but it comes in useful from time to time when attempting to understand things.

I dyno'd my car with some heads that had minor port work done to them. No welding, no enlargement of the ports etc. and no flow bench work. Just a basic port job done by a shop that had never even seen 3.8L Ford heads before. At this time I also installed the cam that is still in the car today, and I installed a home-made FMIC and stock S-Port blower with NO OVERDRIVE. I used the stock blower pulley. In this form the car made about 12psi and made 313rwhp adn 363rwtq on the dyno. This is the car that is represented in the chart below as XR7 1.

Then later I replaced those heads with some "fancy" Steigemeier heads, I added the MP inlet plenum, and I increased blower drive ratio by 10%. In this configuration the blower generated about 15psi and it made 344rwhp and 402rwtq. The dyno chart was posted at the front of this thread and is represented here by XR7 2.

This car is and was one of the fastest cars known to this club. It's not THE fastest by any means but most everyone here has seen this car run and knows how it runs. My only point in saying this is that this car, with 400ftlbs torque and 344rwhp ran a whole string of 12.60-12.80's @ 108-109mph. The car's performance is well documented.

Now then the car tested by Fast Specialties and used to promote the MPIII is in fact very similar to my car. It is a 5spd. It has the advantage of any and all available bolt on parts to enhance performance, and it has ported heads and cam upgrade. This car made 390rwhp and 469rwtq at 17psi. It is represented on the chart as FAST XR7.

Now it has been said that my car has fancy heads that are giving it extra performance at high rpm. I disagree with some as to the real impact of this. If you look at the chart you can see that with the non-fancy heads on the car, torque output at higher rpm pretty much mirrors that of the motor with the added boost from additional OD and a better flowing intake. If the Steig heads really made a big difference I would have expected to see gains in the upper rpm moreso than the lower ones. Instead I see bigger gains down low than up high which is indicative of the blower running out of air as noted in the preceding posts. Nonetheless, the better flowing heads are probably having some impact, but it certainly isn't discernable from the charts.

Maybe you agree with this, maybe you don't. But lets move on.

I do know one thing about the Fast Specialties car. Our cams are identical. 210/220 dur. and .491" lift (.513 with 1.8rr). I did also in fact verify output before and after installation of the 1.8rr's on my car and documented on the dyno that there was no increase in power. Just so you know.

So. With very similar cars and the same cam, my question is, how did the Fast Specialties car manage to make roughly 70rwtq more than my car did at peak torque rpm, but only 35rwtq more at peak HP rpm? Why did the torque advantage drop by a full 50% by the end of the rpm range? I thought the MPIII was a high rpm race blower? Why is it losing tq so rapidly at high rpm?

Look at the chart. Tell me why this is. Because it bothers me that this dyno chart shows frankly very weak high rpm performance yet completely gangbusters torque at lower rpms. And if in fact this is typical of the MPIII's performance characteristics, then why did we not see a similar trend on Dan Sly's car? Surely if there was belt slip on Dan's car at 3000rpm it must be getting worse as rpm increased, no? If it was getting worse or even staying the same, then why did Dan's car outperform mine in the higher rpm ranges while the Fast Specialties car was faltering in the higher rpm ranges?

Again, mine and Travis' cars have the same camshaft. What gives? :confused:
 

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XR7 Dave said:
Kevin, I field questions regularly from new owners of MPIII's who have not achieved the kind of results they expected from their blower purchase. People who will not post here on the website for whatever reason email me to ask what I think. I have answered them in private honestly and directly about what I have seen and what I have heard. None of this involves any product bashing.
I have talked with Kevin, David N about the MPIII's performance. I have left a voice mail with Randy asking him to call me. Of all the others who bought the MPIII NONE have called or emailed me to complain regarding their MPIII's performance. Others outside this club however have called telling me about their scary experiences burning rubber in second gear, etc and they have been very happy with their results.

I find it odd that dissatisfied customers would not call the vendor and complain.
I find it odder that MP customers who want to complain would call Dave D.
I find it even odder they are only people who do not post on this BB.
I find it very odd that Dave D would post such an occurrence here.


Charles
 
Was it the belt that gives?

I personally dont think those fancy heads will do you all that much good unless you are moving your powerband up in RPM's with a cam that can use the extra flow those heads provide.

As far as real street performance goes its all about power under 5,500 rpm's with a built in fun factor. Good low end torque is the fun factor

Regardless of peak power output or 1/4 mile times if you have a 4,000lb car with driver with all its power in the upper RPM's in street trim (3.08 gears, tight converter)...That is no fun at all. Throw some 4.10's and a loose converter and yeah it will be one heck of a ride....Streetable?....Not really.
 
Dave that's very interesting. I don't know if your questions are rhetorical or not, but I do know that you know the answer to them. I'll take a shot at it anyway.

As your graph shows, all of the tq curves dropped off rapidly regardless of the amount of porting done to the head welded or not. It simply show's that the M90 doesn't provide enough cfm in the higher rpm ranges.

Although the MPIII is the best available M90, in terms of CFM, it helps, but it still isn't enough provided CFM to cause the problem with the sudden drop in high end tq as proof.

The FMIC's used also play a role. Dan has a different style IC then the MP FMIC does. He has less and more direct pipe routing than the MP's FMIC does.
 
XR7 Dave said:
Of course comparing dyno numbers will only get you so far, and I suppose in many cases do nothing but get you into trouble, but nonetheless I have a question.

Please follow my logic here.

My car has been dyno'd many times over the years. I have kept the dyno charts and notes of what mods the car had at each dyno session. I have done this for my own purposes only but it comes in useful from time to time when attempting to understand things.

I dyno'd my car with some heads that had minor port work done to them. No welding, no enlargement of the ports etc. and no flow bench work. Just a basic port job done by a shop that had never even seen 3.8L Ford heads before. At this time I also installed the cam that is still in the car today, and I installed a home-made FMIC and stock S-Port blower with NO OVERDRIVE. I used the stock blower pulley. In this form the car made about 12psi and made 313rwhp adn 363rwtq on the dyno. This is the car that is represented in the chart below as XR7 1.

Then later I replaced those heads with some "fancy" Steigemeier heads, I added the MP inlet plenum, and I increased blower drive ratio by 10%. In this configuration the blower generated about 15psi and it made 344rwhp and 402rwtq. The dyno chart was posted at the front of this thread and is represented here by XR7 2.

This car is and was one of the fastest cars known to this club. It's not THE fastest by any means but most everyone here has seen this car run and knows how it runs. My only point in saying this is that this car, with 400ftlbs torque and 344rwhp ran a whole string of 12.60-12.80's @ 108-109mph. The car's performance is well documented.

Now then the car tested by Fast Specialties and used to promote the MPIII is in fact very similar to my car. It is a 5spd. It has the advantage of any and all available bolt on parts to enhance performance, and it has ported heads and cam upgrade. This car made 390rwhp and 469rwtq at 17psi. It is represented on the chart as FAST XR7.

Now it has been said that my car has fancy heads that are giving it extra performance at high rpm. I disagree with some as to the real impact of this. If you look at the chart you can see that with the non-fancy heads on the car, torque output at higher rpm pretty much mirrors that of the motor with the added boost from additional OD and a better flowing intake. If the Steig heads really made a big difference I would have expected to see gains in the upper rpm moreso than the lower ones. Instead I see bigger gains down low than up high which is indicative of the blower running out of air as noted in the preceding posts. Nonetheless, the better flowing heads are probably having some impact, but it certainly isn't discernable from the charts.

Maybe you agree with this, maybe you don't. But lets move on.

I do know one thing about the Fast Specialties car. Our cams are identical. 210/220 dur. and .491" lift (.513 with 1.8rr). I did also in fact verify output before and after installation of the 1.8rr's on my car and documented on the dyno that there was no increase in power. Just so you know.

So. With very similar cars and the same cam, my question is, how did the Fast Specialties car manage to make roughly 70rwtq more than my car did at peak torque rpm, but only 35rwtq more at peak HP rpm? Why did the torque advantage drop by a full 50% by the end of the rpm range? I thought the MPIII was a high rpm race blower? Why is it losing tq so rapidly at high rpm?

Look at the chart. Tell me why this is. Because it bothers me that this dyno chart shows frankly very weak high rpm performance yet completely gangbusters torque at lower rpms. And if in fact this is typical of the MPIII's performance characteristics, then why did we not see a similar trend on Dan Sly's car? Surely if there was belt slip on Dan's car at 3000rpm it must be getting worse as rpm increased, no? If it was getting worse or even staying the same, then why did Dan's car outperform mine in the higher rpm ranges while the Fast Specialties car was faltering in the higher rpm ranges?

Again, mine and Travis' cars have the same camshaft. What gives? :confused:

Travis' SC has a very short duration cam 206/206 and .512" lift. It's the cam that is giving out not the blower. Note the 15% to 20% dyno pull comparisions, the HP went up by 15 hp all along the pull and showed no sign of slowing down at the top end. Boost started off at 14 psi and ended at 17.7psi at the end of the pull, meaning the blower was breathing better then the engine at high rpm.

Charles
 
I will be curious to see how long these MPIII will hold up under 15%+ OD. If I remember correctly the ESM blowers had plates welded to the sides of the cases to prevent flex aswell as the snout shaft was upgraded to titanium. Another asset that should have been offered with the MPIII is coated rotors.

Charles,
Is there anyway the MP III can be improved apon or is this it for the MP series Superchargers?
 
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