overdrive% question

pbdevastator

Registered User
if one has a wide open exhaust, and mp intercooler, and all the other mp goodies, how much overdrive could i safely run without too many problems? right now i have a 5% overdrive pulley, and was thinking of getting the 10% crank pulley.
 
You are going to get to a point that there is more heat and work being done by the engine through the blower then it is worth. Im not sure what it is for the MPII but for the AR on J-Millers car, it did better with the 18 psi jackshaft then it did with the 21-22 psi pully. It made more power by like 20 hp or something like that. Hope this helps.

Chris
 
I had....

I had the same question today and got it answered by Dave Dalke.

It's all relative!!!!!

Let's see, if you have the MPII blower, and all the goodies, and no tune....The book is already written up on you because you are probably running WAY TOO LEAN!!!! I proved this today because the dyno tune I did proved a 13.7-1 ratio that I thought was good from a previous tune. First things first, get a tune......

Second....If you are running 5%, what boost pressures are you seeing. I don't mean at 3000 rpm, I mean at 5000 rpm in a higher gear....12-15PSI????? If this is the case, leave it alone, MPII's don't tolerate the higher speeds that MPIII's will.

I have a stock bottom end, stock heads, medium lift cam, exhaust and all the goodies. I ran 17PSI at 5500RPM :eek: :eek: :eek: This is considered high. It only saw 12 PSI until about 4500 RPM then up went the boost pressures. This was with an MPIII. This was also with 15% overdrive.

Needless to say, without a tune and some more info, no one can honestly answer the question.

As always, I am always available. Give me a call and I will help you with any questions you may have that I can honestly answer.


Don

(973) 277-4294
 
lube70 said:
I had the same question today and got it answered by Dave Dalke.

It's all relative!!!!!

Let's see, if you have the MPII blower, and all the goodies, and no tune....The book is already written up on you because you are probably running WAY TOO LEAN!!!! I proved this today because the dyno tune I did proved a 13.7-1 ratio that I thought was good from a previous tune. First things first, get a tune......

Second....If you are running 5%, what boost pressures are you seeing. I don't mean at 3000 rpm, I mean at 5000 rpm in a higher gear....12-15PSI????? If this is the case, leave it alone, MPII's don't tolerate the higher speeds that MPIII's will.

I have a stock bottom end, stock heads, medium lift cam, exhaust and all the goodies. I ran 17PSI at 5500RPM :eek: :eek: :eek: This is considered high. It only saw 12 PSI until about 4500 RPM then up went the boost pressures. This was with an MPIII. This was also with 15% overdrive.

Needless to say, without a tune and some more info, no one can honestly answer the question.

As always, I am always available. Give me a call and I will help you with any questions you may have that I can honestly answer.


Don

(973) 277-4294

Don,

How much power did your car end up making ?

David
 
well the computer is not running the stock program, dave has made a chip, its not a dyno tune, i kept meaning to goto a dyno to get a airflow ratio, but i figured i'd wait till the headgaskets blew and do the dyno after i put some better heads and cam in, and at that point wanted to do the 10% crank for a total of 15% overdrive. right now the car is running awsome, kinda hate to mess with it more, but i want it to be faster. to answer your other question, boost gauge tops out at about 12 psi.
 
My point was different. I was assuming there was a tune. At SOME point, you are going to be trying to overdrive what the blower is able to produce. At that time, it will still be moving air, but you will be losing more power then you would lose with less boost and making more engine power. Then you would need an upgrade on other things. Higher cam, ported heads, exhaust, etc...See?

Chris
 
think so, your saying i should go with my first instict which is wait for the head gaskets to blow which could be any mile now, then when i change those along with better heads and cam with some kind of lower intake manifold port, put the 10% crank pulley in at that point, then get a dyno tune. my better options now
i'd assume would be tranny work and rear gears and such at this point. thanks for your help.
 
David..

Car made 312hp at the wheels. Considering that I am basically out of injector now (running at 90% duty cycle) and at 5200, I lose A/F ratio of 11.5 and it rises to 12.5 and climbs. Next is trying to run more fuel pressure (my fault, didn't tell Dave about AFR) and try to get some more out of it. It was still climbing at 5300 when the boost pressures were around 17-18lbs and I got nervous and stopped the dyno guy from going higher. Might have made a few more hp but I am completely happy with that for now.

I am actually looking at doing an A/R kit on the SC to see what difference I can get. My problem is I need heads to go further. Right now, stock bottom end except for cam.


Don
 
Don,

312 rwhp is actually very impressive for stock heads. I've see several CMRE stage II motors that didn't make that much.

I think it's a good idea to install the ported heads before the AR. BTW, your gonna love it.

David
 
I have....

Flex said:
Don,
What are your mods to date?


I have a stock long block from Ford (great headgasket warranty!!!!), rest of mods are in the profile. Nothing to hide here....

.538 lift cam, 1.73 roller rockers, headers, full exhaust, MPIII blower and plenum, 5% blower pulley, 10% jackshaft pulley, SCI pulley stock size set, 255 FI fuel pump, 42 lb injectors (out of injector at this point, time for 50's), +L 76, BBK 75mm TB, blah, blah, blah....


Hey David, our own Jim O'Neill (not related!!!!) ran today a 391RWHP and I think 428 RWTQ with the A/R set up. Dave had a bitch of a time tuning the MAF and getting it right. These numbers were AFTER running 7 (yes SEVEN!!) dyno runs!!!!!

Hopefully, he'll break over 400 on a colder day and a cold motor.

We'll post up the dyno sheets soon. I've got to get an A/R!!!!:D


Don
 
pbdevastator said:
think so, your saying i should go with my first instict which is wait for the head gaskets to blow which could be any mile now, then when i change those along with better heads and cam with some kind of lower intake manifold port, put the 10% crank pulley in at that point, then get a dyno tune. my better options now
i'd assume would be tranny work and rear gears and such at this point. thanks for your help.


If you blow the gaskets, you might blow the bottom end as well. Nothing says that just replacing the gaskets at that point will be OK. I would just change out the gaskets, do the mods, get a tune, and be done with it.

I tuned my 94 auto today (basically stock except for the MPII blower and inlet, headers and exhaust (heck, still have stock intake!!!!), and ran a 258RWHP finally after the initial Air/fuel ratio of 15.4-1!!!! That's dangerously lean!!!!!! Thanks to Dave for recommending me to tune it for a/f or I might have had some issues myself!!!

Again, I cannot stress enough...DO NOT JUST RUN IT TILL THE GASKETS BLOW!!! That's engine suicide!!!


Read the forums, take the advice of people like David Neibert, and Dave Dalke and others and do the right thing.

Don
 
Back
Top