Limited to race fuel only!!

[svo/svt]

I've just finished my cobra build and I'm plaining on getting it tuned now and running in to a big problem.

The new setup is a mmr 5.0 stroker with 11cc dished piston. I'm running a whipple 2.3 with a 3" pulley and stock lower I have all the supporting mods. Return fuel,60lbs,jlt and full exhaust with long tubes ect...

I'm being told because of my 11cc pistons that the compression will be to high and I will be limited to race fuel only (100 octane).
Not staying the tuner is wrong but because I'm in Cali I'm limited to 91 fuel and he said he will not be able to provide a safe street tune.
I mentioned putting a larger upper pulley on and he said it would not be enough of a change to help.
I want to enjoy my car and not be limited to track use only.
Is there anything else I can do other then swap out the Pistons for some 18 or 20cc ones?
Any advice would be really appreciated as I'm bummed out about the whole build with the thought of swaping Pistons
Thanks.

 

[01yellercobra]

What's your compression?

 

[Michael Hughes]

First I need more info on your engine? port/polished heads, cams, head gasket thickness ect to determine you CR.

Ball parking it using a stock engine 03/04 engines specs (95 mm bore) puts you around 10.5:1 I think.

What I would do If I was in your situation:

1. Increase the the Blower pulley to a 3.5" that should drop your boost to around 13 psi (using a stock crank pulley).
2. Decrease the crank pulley to a 6.5" this should drop your boost to 9 psi (with a 3.5" upper pulley installed).

I would start here with car. I would try to tuning on 91 fuel with 10.5:1 DR and 9 psi of boost. If you run in to detonation problems while tuning I would try adding Torco fuel addictive, or a Water meth system to eliminate the detonation. If this fails (91, Torco, Wate meth) do you have E85 around you?

 

[Riddick]

You are a perfect candidate for E-85. What does your fuel system consist of? You will definitely have to ditch the 60s and get at least 80's if you switch to E-85. If you are limited to race fuel only thats going to take a toll on the old wallet!!

 

[svo/svt]

So I'm running stock heads/cams and intake. My head gaskets measure at .41 and my pistons are Manley 595100c8 and it says on Manleys specks it should have a 3.552 bore. I'm in sure as to what the compression ratio is.

As for a fuel system I'm running 2 ford gt pumps in a billet fore hat.

I wish I could run e85 but I live way up in northern Cali and no ones sells it.

 

[Brutal Metal]

First I need more info on your engine? port/polished heads, cams, head gasket thickness ect to determine you CR.

Ball parking it using a stock engine 03/04 engines specs (95 mm bore) puts you around 10.5:1 I think.

He's definitely not at 10.5:1 with 11cc dished more like 9:1

 

[Brutal Metal]

I've just finished my cobra build and I'm plaining on getting it tuned now and running in to a big problem.

The new setup is a mmr 5.0 stroker with 11cc dished piston. I'm running a whipple 2.3 with a 3" pulley and stock lower I have all the supporting mods. Return fuel,60lbs,jlt and full exhaust with long tubes ect...

I'm being told because of my 11cc pistons that the compression will be to high and I will be limited to race fuel only (100 octane).
Not staying the tuner is wrong but because I'm in Cali I'm limited to 91 fuel and he said he will not be able to provide a safe street tune.
I mentioned putting a larger upper pulley on and he said it would not be enough of a change to help.
I want to enjoy my car and not be limited to track use only.
Is there anything else I can do other then swap out the Pistons for some 18 or 20cc ones?
Any advice would be really appreciated as I'm bummed out about the whole build with the thought of swaping Pistons
Thanks.

I can see your compression being that high (10.5)with a flat top but this tuner said an 11cc would be impossible to tune on 91 pump? Even with 12 degrees of timing and an 11.0 A/F? haha find a new tuner man... FYI the 11cc is a common off the shelf offering from all the top piston makers..

 

[Wiseguy]

Depending on the deck of the block and milling of the heads. You are at 9.1 /9.3.1 and would be fine on pump and not required to run Race gas all the time. Bump in compression allows you to run less boost and be safe on low octane.

 

[encasedmetal]

your tuner is wrong. I and plenty of other setups are running higher compression on pump gas

 

[01yellercobra]

I'd find another tuner.

 

[Weather Man]

Total BS from the tuner.

 

[Quick Strike]

I get about 9.7:1 static compression with a stock head CC and a .006 piston to deck clearance (a good estimate of the amount needed to square the deck). This will yield roughly 9:1 dynamic compression with the stock cams degreed in the stock location. Pump 93 octane fuel likes 8.25:1 dynamic compression or less for the best detonation resistance in a cool running engine with good combustion chamber features and adequate quench. I think you will be detonation prone unless you add octane (Torco or E85) or reduce dynamic compression with a later closing intake event (more cam duration and/or more retard in the intake setting).

 

[98 Saleen Cobra]

Who is the tuner?

 

[brady_f]

i'd find another tuner.

x2

 

[svo/svt]

The tunner is Shaun from Aed and I know he's praised for he's tunes. He's hard to not take serous since he's suppose to know his shit. The engine was built by mmr. I bought the engine with less then 8k on it from a friend who had a vortec supercharger on it. He claims he made 535 to the wheels on 14psi. The friend I got it from wrecked the car so I got the engine for $3k. I wish I could ask him more questions about the tune that was on it but he moved away and I don't have his number. He said his power was limited because he was running 42lb injectors and a stock maf.

 

[svo/svt]

I live in eureka ca and he is the only tunner I know of and he's 6hrs south of me.

 

[Brutal Metal]

The tunner is Shaun from Aed and I know he's praised for he's tunes. He's hard to not take serous since he's suppose to know his shit. The engine was built by mmr. I bought the engine with less then 8k on it from a friend who had a vortec supercharger on it. He claims he made 535 to the wheels on 14psi. The friend I got it from wrecked the car so I got the engine for $3k. I wish I could ask him more questions about the tune that was on it but he moved away and I don't have his number. He said his power was limited because he was running 42lb injectors and a stock maf.

I'm not sure why he says he couldn't tune it, I'm sure he's done Tons of safe pump gas tunes?

 

[gabe1530]

another option is to buy a 5 gallon drum of torco and cut in 32+ (or more) ounces with each full tank. this way the octane is high enough that Shaun will be comfortable tuning it (actually, check with him first). you will also have to decrease the boost as well.

 

[svo/svt]

Here's the email I sent Aed and his advice. He recommends a piston change.
I can switch pistons if I have to as i can afford to run race gas every day.


I have a 99 cobra. I'm plaining on
bringing you my cobra for a tune but I live 8 hours north and I'm
hoping you could look over my setup so I can address any problems
before I
bring my car.
You sent me a tune to get the car running with a return style fuel
system a few years ago and Ive just got the car finished.

My setup

Engine
mmr 5.0 stroker with 11cc dished Pistons, arp head studs, stock heads
and intake manifold

Supercharger
Whipple 2.3 with single blade throttle body. I have 2 pulleys 3.5" and 3"
with a stock lower. It has a large heat exchanger also.

Intake
Stock intake tune and stock maf in a 100mm housing with a large open
filter.
I have a mafia if needed.

Fuel
Return style fuel system with twin 255lph pumps and 60lb Siemens
injectors.

Exhaust
Long tubes with off road x and borla stingers.

Ecu
Sct xcal3 and a dyno jet wideband.

If you have any concerns please let me know. My main goal its to get
600hp.
I'm not appose to doing a race gas tune if needed but I'm unsure as
to what octane to use.

Thanks for your time
Dennis.

Dennis,
Your compression is too high for a pump gas tune.

Shaun
AED

Thanks for the response. Any recommendations as to which octane to buy.
100,104,110? Will there be anyway to have a street tune to work with
pump gas if I run a stock whipple upper?
Thanks.

Given the compression ratio of this new engine there is no way for me
to give you a *safe* tune to run on pump gas. You cannot lower boost
enough with this blower application.

Shaun
AED

Would 100 unleaded be a high enough octane?
Would you recommend switching the Pistons out for 18cc ones?

18-20cc dish would be acceptable, or 100 octane unleaded would be fine with
the current pistons. There are a few variations on 100 octane however, some
are far better than others, but all will be OK for this application.

Shaun
AED

 

[svo/svt]

I totally understand gabe1530 I wouldnt want to risk it either if it wasn't safe. I would not be against running a mix as it would be a hell of a lot cheaper then running pure race fuel all the time. How much boost would I be limited to. I was doing some research and with a 3" pulley and a stock lower I should be around 16-17 psi I think. My main goal is to a least hit 600hp. At the local street drags there's a punk in a new zr1 camaro that his daddy bout him and he thinks he's unbeatable and I want to crush him.