HP and Torque Question

hytorksc

Registered User
I know SC's are primarily low end beasts and not built for all out sports car street competition, but what i would like to know is if you wanted to dramatically increase acceleration to real sports car like levels and make a broader power band (expanding mids and top end power), would it be a good idea to open up and upgrade head components, and install a 10% (or more) OD pulley, a flowing exhaust system, and say 4.10 gears on an AOD?

I'm not planning to run the car beyond 120mph, all i want out of this thing is the ability to beat up other sports cars on the street- so is there any reason why I shouldn't do this? I calculated that my rpms will increase by 750 over stock at highway speeds roughly, and this will put alot more leverage or force in lbs at the wheels.

For example, let say a typical stock Viper can put down this (hyperthetically);

(engine torque x (trans gear ratio x diff. ratio)) x 0.80=wheel torque (??)

Viper-
500ft lbs x (3.00 1st gear x 3.55 diff.) x 80%=4260 ft lbs force at wheels (4000 rpm)

SC (estimate-mine after above mods)
420ft lbs x (3.00 1st gear x 4.10 diff.) x 80%=3936 ft lbs force at wheels (2800 rpm)

Well.. I guess the viper would still be slightly faster off the line primarily because of it's higher rpm- the SC would drop off somewhat (not badly) past 2800 rpm.
So i guess the objective is to get as much HP and torque spreaded out up high around 3000 to 6000 rpm and then gear it up as high as possible to be able to come close to those other extreme sports cars- adding MUCH big power at higher rpms is the key for the SC to overtake (weight included). Somehow i think the supercharger drag, weak heads, and crank are the limiting factors with achieving that.

You know I'm not sure that equation above is correct either.

Anyone please share your thoughts-
 
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Another factor to consider in acceleration is mass, and the SC has much more of it than a Viper.

From what I always understood, one major thing that limited the SC to a lower RPM performer was the redline and efficiency range of the blower. Adding a 10% would lower that. Due to that constraint Ford designed the rest of the engine (heads cam exhaust etc) to be a low RPM brute.

If I was serious about making one of these a higher RPM screamer, I would seriously investigate replacing the M90 with a turbo. You lose the RPM limiting of the blower, and you gain back the ~70HP parasitic lose to drive the M90.....Then again we have started down this road before.
 
420 ft-lbs of torque? Keep dreaming, you'll need a lot more than heads, 10% pulley, and exhaust to get 420 ft-lbs. Check the shootout results to get an idea of the torque people are making. 420 ft-lbs would put you near the top of the list...

But you have the right idea with gears, although 3.73 is the most popular for automatics. Changing gears made my car feel like it was 500 pounds lighter. BTW I went with 3.55 because I didn't want to run out of 3rd (D) in the quarter mile. With 3.73s I would have to shift into OD and that just wouldn't work.

Especially if you go to 4.10s, you'll probably want to get an aluminum driveshaft, because with the much higher driveshaft RPM's you'll notice how badly balanced the stock shaft is!
 
I thought about turbos too, but you would have to boost that v6 at like 25 psi to get that lead to haul and gear it pretty high to overcome the weight- then you have to play with lag (getting the right sized turbo) and fuel octane issues (hitting 600hp barrier on pump gas). The only car i have seen do extremely well with turbos are the Mark 4 Supras.
 
Well Rob...

I guess the SC no matter what you do to it, if it still has an m90 style supercharger on it, it will always be limited in achieving extreme performance. Although i have noticed what Coy and Fred are doing as well as Chris and Dave Neibert- i believe they are trying to work around the design constraints that Ford put on this car and they have done quite well.

Someone really needs to take the Ford v6 and re-design the heads, bulletproof the bottom end, and develop a quick spool single turbo setup that won't blow the v6 apart. Get the heads to flow and take 22+ psi of boost, AND, gear the rear up high to lay down maximum leverage and keep most of the low end response- the SC would have arrived then. But then some here would say it's not an SC anymore if you do this. i still think it would be- just improved to the extreme level. Reliability will suffer?? well... who knows.

So who wants to step up to the plate and do this $$$$$$$$ :eek:
 
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hytorksc said:
I thought about turbos too, but you would have to boost that v6 at like 25 psi to get that lead to haul and gear it pretty high to overcome the weight- then you have to play with lag (getting the right sized turbo) and fuel octane issues (hitting 600hp barrier on pump gas). The only car i have seen do extremely well with turbos are the Mark 4 Supras.

Yeah I agree, the weight of our car doesn't lend itsself to a turbo application very well. But your original post seemed to hint at taking the SC out of it's conventional performance arena. To me that means unconventional performance through unconventional means. I'd be very curious how a twin setup would work for us. I'd maybe start with the turbos used on VW/Audi 1.8L motors. Those engines are capable of some good numbers, our engine is roughly twice the size so two of their turbos would be about right.

Now specifically I was thinking of drawing form the Buick Grand National folks. (forget the Supra) Since their basic engine design is pretty similar to ours, and they have proven quite a bit of performance from a 3.8L V6 (easily enough to pass up Vipers). Their basic theory and Turbo sizing would probably work quite well for us. With an alcohol injection kit the high PSI without HUGE octane numbers doesn't seem to be a problem.

I think our bottom end is stronger than theirs stock. I don't know about how the heads compare, but I think, properly ported, ours flow pretty damn well, probably better than the Buicks (at least the stock ones).

But if we are ditching the M90 and going turbo, there is nothing preventing the use of the '99+ split port heads which can flow even better. Probably a better starting point would be the Ford Grand National / SVO block and heads...... Now we are really dreaming.

Honestly I think we could pretty realistically imagine Chris Wises numbers + 100 with a turbo setup on a motor built like his for a starting point. I am hearing tales of 1000+Hp, sub 9 second street Turbo Buicks, and I really don't see why we couldn't someday match them....But we will pass the limits of the M90 long before then.
 
Now specifically I was thinking of drawing form the Buick Grand National folks. (forget the Supra) Since their basic engine design is pretty similar to ours, and they have proven quite a bit of performance from a 3.8L V6 (easily enough to pass up Vipers). Their basic theory and Turbo sizing would probably work quite well for us. With an alcohol injection kit the high PSI without HUGE octane numbers doesn't seem to be a problem.

Now that i think about it- the grand national would be the pattern to follow because it's a similar setup like you said and that car has almost the same mass- i think it's 400 lbs lighter. excellent idea!!

One question though would be how much boost will our stock SC engine components take after reworking the heads? You still would have to boost it high at least 20+ psi and gear it high to recapture most of the low end response of the original m90 setup. You'd have to aim for at least 400-500rwhp- and even then if you gear the differential high you're talking a 6 speed tranny or a high stall AOD with a kit.
 
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Why bother with designing a turbo for the Ford 3.8 SC block, just fabricate some engine and tranny mounts and stick a Buick turbo V6 and a TH350 in there! Waaay easier, plus then you'll have all the turbo Buick aftermarket parts available, and you can annoy both Ford and GM fans alike with your bastardized Forduick.
 
The idea is to keep it Ford.... We will be the ones to develop our own turbo setup and still use most of Ford's electrical components. It couldn't be much harder at the very least than just installing a new intake/exhaust manifold configured for the turbo, adding oil supply lines to the turbo, add oil coolers, wastegate, bigger injectors, bigger MAF.... wait i just thought of something- this may not work well because Ford uses a hot wire MAF that would be extremely sensitive to turbo surge. It may not handle that very well idle-wise. If the turbo is mounted behind the TB or in front of it, there may be MAF voltage issues.
The grand national i believe uses the speed density setup, so you would have to figure out a conversion setup for Ford. Big time fuel mapping issues... Maybe all of this is a wash- hell i don't know...

I think you're right Rob- especially since i am on a budget.
 
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With enough work you can make a 3.8 liter M90 equipped SC quick enough to hang with Vipers and beat stock Z06 vettes without using nitrous. Mine will do that now. Stroke and bore the same engine to 4.3 liters and add a big liquid IC like Chris Wise did and now your knocking off Vipers.

If I was going to do a turbo SC, and BTW I've been thinking seriously about it, I would not limit the power by staying with 6 cylinders. Instead I would use an EFI 5.0 V8 and make the job a whole bunch easier. I would also use a 93 SC as the platform because of better brake system, spindles that will accept larger brakes and because it's lighter.

David
 
thin ice of the m90

I'll walk on it ...example... a Roush 302 mustang V8 with a m90 .. has nearly a 100 cubes more volume and 2 spare cyclinder and a higher RPM with a bigger bore [4.00 in.] ...over our 232 cubic v6 ....with a m90 ..that can't breath ...with the same stroke ..3.39 inches ..and a smaller bore [3.81in.]....so I ask myself ..where is the problem ...my answer to myself ... must be the heads...not about to ditch the m90 ...believe there's more.. to be untap from it yet ...dave
 
Someone really needs to take the Ford v6 and re-design the heads, bulletproof the bottom end, and develop a quick spool single turbo setup that won't blow the v6 apart. Get the heads to flow and take 22+ psi of boost, AND, gear the rear up high to lay down maximum leverage and keep most of the low end response- the SC would have arrived then.

I know you are just learning, but this statement is just plain off base.

Some facts about the 3.8, the 5.0, turbo's and the SC.

Heads. First of all the heads on the Ford 3.8 are already vastly superior to the 3.8 Buick. No one needs to rework them more than has already been done. If the heads flowed any more then low end torque would be sacrificed in a big way.

Block. With the addition of a stud girdle the 3.8 is already virtually bulletproof. Billet steel cranks are already available that allow stroking without sacrificing reliability. No one has ever "blown apart" an SC block.

Turbo. There is no need to develop anything here. It's already there, you just need to use it.

Boost. The M90 is designed to operate at 8psi of boost. After 18psi it becomes nothing more than a heat pump and ceases to function as a forced induction device. It is also a fact that as a positive displacement blower, the M90 does not perform well on a larger displacement motor. It just doesn't move enough air. It is commonly known that 18 psi is achievable on pump gas (with a proper turbo or blower) and 24psi is common on race gas. Alcohol injection will help achieve 21psi or so on pump gas.

5.0. With the proper parts the 5.0 can displace up to 440ci. The Dart block is good to up to 1500HP (maybe more) in that configuration. The Mustang guys have already proven what that combination is capable of, there is nothing to prove there.

SC. The SC is not that heavy. I believe that the GN is about 3500 lbs. My XR7 weighs 3525. Addition of skinnies, a tubular K member and the removal of some useless interior junk would make 3300 easy. I don't even have any aluminum IRS components (yet).

Intellectual discussions are fun, but before you put out a challenge to the SC community there is some homework for you to do. There is already an SC motor out there making over 1500HP. You figure out what car it is running in. ;)

Cheers! David
 
XR7Dave,

I am assuming the "1500hp" SC engine is in one of your cars by the way you were talking. So my previous understanding of the m90 was that it could not put out very high boost effectively because it loses efficiency big time if you spin it very fast. what i would like to know is how can you get the 3.8 over 1000 hp (or 600 for that matter) using an m90? how can it be done without beating the heck out of and nearly destroying the pistons, rods, and crank? wouldn't you have to make the engine process an extremely high volume of air at very high rpms to get it to do that since it's only 3.8 liters?

You're right i am just learning by observations and some experience- i have never built an engine before. However, i have done some tuning which i think works extremely well with my SC. Most of what you call my "challenge" to the SC community is just my way of communicating as best as i can with what knowledge i do have. in some cases i will admit that i don't know how to ask for what information i'm looking for and these posts will reveal my lack of knowledge or understanding of the subject, but i'm trying to learn about these things so i have to post in this way. we all have differences of opinion which is the great thing about this forum- there's always something left to be uncovered.
 
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I got a little confusing with my post. Sorry.
I am assuming the "1500hp" SC engine is in one of your cars by the way you were talking.
Certainly not! Only in my dreams. It runs in the NHRA Sport Compact series and it most certianly does NOT run an M90 blower. It is twin turbo'd, bored, and stroked.

I tried to explain in the paragraph above that how the Eaton blower simply cannot perform past a basic level. Incidently that is one of the reasons that the OEM likes it so much. They know that it is not easy to "turn up the wick" so to speak on the blower. It just won't do it.

What I was really trying to say is that the R&D needed to build a monstrous SC motor has already been done. We (generally speaking) simply don't have the resources ($$) or inclination to make it happen.

It's either really neat or it's really depressing when you think that a backyard mechanic wannabe with no money at all to speak of can make the top 10 ten SC's list. You can't say that about any other performance vehicle that I know of. :/
 
How fast do you guys race on the streets?!!?

I can only count a couple very rare occasions where I could race someone to an endless mph (and we both stopped at 100mph), but for the most part, if you have a car set up for the 1/8th mile, it will kick azz on the street.

You don't need an 8000rpm redline or 600HP to do that either. All you need are some drag radials, put the SC on a mild diet, and get some 1.6-1.7 short times.

Dave, if you ran up against a "typical" ZO6 or Viper, or 03 Cobra.......how do you think the race would go if you were on rubber and got cut a 1.6 short time? I'm betting you would be the winner of that race until you let off.

Traction + torque can be your friend.

Did you have some other kind of racing in mind where you really need to wind the SC out?

Micah

P.S. And to brag about Dave some more....he's got just a plain ole high mileage bottom end and some really good mods around it. Aside from some creative pieces that he fabbed, his performance could be achieved with bolt on parts.
 
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Hey XR7Dave,

What did you think of my idea on the other board. I'm surprised you didn't give me your opinion on whether it would work or not.

Are you mad at me for not racing my car. :p
 
A combination that works in other areas but I don't have the $$$ (or time) to make work.....

Slow spinning M90 + fast spinning cent. blower = ^^^ HP. Yes... it will work... just not very easy to package. Someday I'll try it and see.
 
XR7 Dave said:
Addition of skinnies, a tubular K member and the removal of some useless interior junk would make 3300 easy.

Cheers! David

The stock K member only weighs about 65lbs. It's the rest of the front suspension that is heavy.
 
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