How much BOOST can I run on pump gas?

[Boosted-Cobra]

I am trying to figure out a safe boost level for my 5.0 with a forged bottom end.
I would just call the engine builder and ask, but he had a stroke and closed his shop, Randy Richie at Performance Associates in San Dimas Ca...
The car used to have a smaller pulley, but I have no idea where it is now...

I currently have a 4 inch pulley making 8 pounds on the pillar gauge using a V-2 Vortech.
How far can I safely go with the boost I wonder? on pump gas?

I do have aluminum heads, but no intercooler.
And no idea what the compression is either, but the motor was built for the supercharger.

Vortech says they put 10 pounds on stock engines with pump gas.

My motor dyno'd 430 at the wheels back in 2001... before the 4 inch pulley.

Any ideas what pulley I can get and keep it safe?

Vortech said each pulley size down is worth about 1 to 2 pounds of boost.
3.8" making my boost 10 psi and a 3.6" making it 12 psi maybe...

Comments?

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[encasedmetal]

really depends on your CR and timing-but with no intercooler...eesh

 

[96dreamer]

stock block? don't the 5.0 blocks start having issues splitting around 500?

 

[Boosted-Cobra]

I don't remember the CR, wish I did.

I think there is a girdle on the mains... Again, I forgot. But you are correct, 500 is the limit on a stock block.

I know I sound a bit ignorant about this engine, but in my own defense - I have built several other supercharged engines since this one that was built 15 years ago.



I really hope somebody can chime in here about boost on pump gas here.

 

[Boosted-Cobra]

Doesn't any body here run boost on there 5.0???
How much boost do you have?

 

[cbrown9064]

My buddy runs a Vortech on his Fox 5.0, and he seems similarity equipped. He is getting about 6psi through a CX Racing intercooler, so not really comparable, but he feels he is at the limit without raising the heads.

The answer to your question is a smart assed "until it detonates". I really think you are pushing the limits on your current set up, without cooling the charge. If you don't want to mess with an intercooler, methanol would be an answer.

We also don't know how much timing you have in it.

So many variables...

 

[98 Saleen Cobra]

It really depends on what the compression ratio is.. With it being non intercooled, your going to have heat issues and more likely to detonate at a given level of boost. Boost is heat. It also depends on the octane you plan on running.. 91/93 is a big difference.. Here is what most of the top tuners do for INNERCOOLER cars

8:5 Compression (04 Cobra) with a typical 2.9 etc on 91 is 15psi with about 19* of timing to be safe..

For 93 octane some get away with up to 19psi but that's on borrowed time imo and the timing is sitting around 17*..

Again that's for a 04 Cobra setup.

 

[ImThatGuy]

What type of aluminum heads are you using, CC's? Cam? If your motor was built for a blower its probably around 8:5:1'ish area. You could bump it up too 10 since you have Cali 91 octane, but with your stock block it will be on borrowed time.

 

[Que]

when you raise your compression ratio does that then limit your amount of boost you can use? Example Cobra motor your refering to with 15 psi 91 octane and 8:5 what if you go 9:5?

 

[Boosted-Cobra]

I Have Brodix heads, CC unknown...
Roller cam with a lumpy idle, but revs quick so I don't think there is very much overlap.

I am actually in Nashville and gas is 93 here.

 

[98 Saleen Cobra]

when you raise your compression ratio does that then limit your amount of boost you can use? Example Cobra motor your refering to with 15 psi 91 octane and 8:5 what if you go 9:5?

Yes.. The boost would have to drop to compensate for the added compression, unless you're running higher octane or E85.. The other option that I've seen is them decrease timing..

 

[2DXTRM]

Whats the end goal power wise?

Whats the fuel system setup (injector size, fuel pump size, what size fuel lines)?

What is being used to tune this car (hardware (chip)/software and what size/brand MAF sensor) and who will tune it?

You can also make a little more boost/power by replacing the stock Vortech blower inlet tube and getting an Anderson Powerpipe.

 

[Boosted-Cobra]

I want to make a small move toward the original tune, without having to have another complete tune done.

The power seems pretty low with the 4 inch pulley on the motor now.

I have the complete and original tune minus the pulley on the supercharger (lost it in the move): 24 injectors, t-rex fuel pump and the vortec Fuel Management Unit, with the custom tuned Super Chips computer chip and the MSD boost retard which has the retard nob glued to ZERO since the chip handles that. No idea what the timing is set to. Just like I don't know the compression ratio...

The local shop here wants to update my system and remove the FMU, switch the 24 injectors to 42 injectors and run a new maf and a new TCS chip, with a new tune that he would program on his dyno for $2000.

DELK Performance here in Nashville.

Basically, either spend $2000 to set it up using modern methods and really know that it is safe,
OR I could just switch the pulley to make 10 or 12 psi and GUESS that it will be O.K.

Still trying to decide: $2000 or a pulley for $80...

The motor has around 5000 miles on it since built in 2001, it is still like new.

 

[Boosted-Cobra]

I am going to have my storage searched for the old receipts and paperwork on this engine.

I hope it turns up.

I don't like rolling the dice and don't want to risk detonation on the motor.

But I am still interested in what others are running for boost with a 5.0 on pump gas. Anyone?

 

[Tabres]

If it were me I would fork over the $2,000 and get it running properly and safely. That's what you're going to spend on another motor anyway when this one blows because you messed around with it without knowing anything about the setup.

To be fair, I can't see why those parts and a tune should cost $2,000. The parts are pretty inexpensive and they're easy to switch out on your own. Do the leg work and let them tune it and you'll be all set.

 

[Boosted-Cobra]

If it were me I would fork over the $2,000 and get it running properly and safely. That's what you're going to spend on another motor anyway when this one blows because you messed around with it without knowing anything about the setup.

To be fair, I can't see why those parts and a tune should cost $2,000. The parts are pretty inexpensive and they're easy to switch out on your own. Do the leg work and let them tune it and you'll be all set.

You are probably right about swapping the parts myself and getting the tune done.

I would hate to lean out this motor.

I am pretty sure that my crank shaft alone cost $2000.

The crank billet was selected from several raw billets.
All billets were represented by images printed out, in actual size.
They were sonograms, or x-ray images (forgot how this is done) to see the metals grain pattern, like wood, sort of.
The engine builder selected the billet he liked best and the crank shop turned it to his specs.
Custom crank shaft...


Hate to ruin it...

 

[Shake&Bake]

I want to make a small move toward the original tune, without having to have another complete tune done.

The local shop here wants to update my system and remove the FMU, switch the 24 injectors to 42 injectors and run a new maf and a new TCS chip, with a new tune that he would program on his dyno for $2000.

DELK Performance here in Nashville.

Basically, either spend $2000 to set it up using modern methods and really know that it is safe,
OR I could just switch the pulley to make 10 or 12 psi and GUESS that it will be O.K.

I would ditch that FMU and for sure go bigger injectors. Also I was always told anything over 10 pounds of boost needs some sort of intercooler, but not sure that only pertains to us Modular guys. Honestly I wouldn't think twice about spending the money to make that car right. Looks like a really nice clean Cobra.

 

[Boosted-Cobra]

Thanks for the compliment.

Here is a picture of the car.

I need to clean it.

How much boost are you running on pump gas?
Anyone?