Am I underspinning the blower?

[GT 11B]

i just recently picked up an 03 cobra. With a 3.4crusher that was recently put in. Also it was set up with 93 and e85. I've been reading about what amount of boost i should be putting out and what size pulley. But it's not adding up for my car. According to the boost guage I put out 16 lbs on a 3.5 in pulley. I think it's too low. What size pulley would I need to get to 24ish lbs? It has a stock lower and long tubes. Is under 20lbs underspinning blower? It puts out 576 rwhp on 93 and 682 on e85.

 

[Bdubbs]

Way to much blower for the boost level. I can't imagine it hits hard down low like a smaller blower would. personally I'd sell it and step down to a 2.9 whipple. Unless you have plans of building a motor for 25+ psi.

 

[TRBO VNM]

Unless you are running e85 all the time or higher octane unleaded/leaded fuel, the 3.4 is a waste of a blower for the street on 93. You would get more enjoyment from a 2.3 or 2.9. The 2.9 is probably about the largest I would even consider if I were running 93 and even then I wouldn't do it unless I could run e85 all the time.

What gauge are you looking at for the 16.5#? Are you sure that is accurate?

 

[GodStang]

I have a buddy looking to trade for a 3.4L. He has a 2.8L with behemoth inlet. Great blower he is just built running E85 so the 2.8L is too small for him.

 

[GT 11B]

I run e85 when I can because it's cheaper but I think the tune isn't just right. And yes the bottom end torque sucks. I want to put it up to 24-26 but Idk if he motor can take it. I had a 2.3 whipple on my 05 and it was way more aggressive. I deffently would like to add more boost but don't want to blow the motor

 

[GT 11B]

Also it's a digital guage and I had my tunner on while I was pulling and its accurate

 

[Bdubbs]

I run e85 when I can because it's cheaper but I think the tune isn't just right. And yes the bottom end torque sucks. I want to put it up to 24-26 but Idk if he motor can take it. I had a 2.3 whipple on my 05 and it was way more aggressive. I deffently would like to add more boost but don't want to blow the motor

My understanding is anything over 23 psi head studs are recommended.

 

[GT 11B]

I'll have to check it out. Ripping the heads off is a pain.

 

[MG0h3]

Im surprised youre only seeing 16 on a 3.5 at sea level. On manifolds it would be 17-18.

On my 2.9, the 3.5 was 17psi at sea level on manifolds.

If youre sure the gauge is correct, definitely pulley down and retune. Id try a 3" pulley. Probably put your around 21.

 

[c6zhombre]

All the 3.4 boost charts I found on line say the 3.4 whipple with a stock lower and 3.5 upper are suppose to be 23psi. That's a ton of boost for 93. You need secondary verification of what exact psi you are putting out if you are unsure that gauge is accurate. Most 93 octane setups I read say they run a 3.875 with stock lower. E85 could use the 3.5 or 3.25 upper.

Might be time for 2 retunes as well...one for the corn and one for the 93

 

[MalcolmV8]

The 3.4 is to big for pump gas. Even my 2.9 crusher setup was a slouch on pump gas. The pulley / ported eaton setup prior was much more fun on pump gas.
The bigger blowers need some octane, race fuel, E85 etc. so you can crank up the boost and timing and then they come to life.

 

[ctgreddy]

I'd put another gauge on it and see what it says. We did a stock engine 3.4 crusher car that had a 6.55 lower(smaller than stock) and a 3.625 upper that made 20psi. On 93 it made 630. With a stock lower and 3.5 upper you should deff be seeing 22ish.

 

[TRBO VNM]

All the 3.4 boost charts I found on line say the 3.4 whipple with a stock lower and 3.5 upper are suppose to be 23psi. That's a ton of boost for 93. You need secondary verification of what exact psi you are putting out if you are unsure that gauge is accurate. Most 93 octane setups I read say they run a 3.875 with stock lower. E85 could use the 3.5 or 3.25 upper.

Might be time for 2 retunes as well...one for the corn and one for the 93

And this is why I was wondering about the gauge being used. I have never heard of a 3.4 being that low with the 3.5 pulley. I thought out of the box they were 20+. So right now I would say something else is up.

OP, what vacuum are you seeing? Are you sure of the pulley sizes? I know the whipple pulley is typically marked so I assume that is what you have, the lower pulley, are you sure it is stock?

 

[MalcolmV8]

For reference my 2.9 Crusher setup on the stock 3.5" pulley with a stock lower made 20 PSI with stock manifolds. Your 3.4 should be more.

 

[GT 11B]

Well there is a dyno day this weekend. So I'll be able to tell exactly what numbers and what boost it puts out. According to the guage and the hand held tuner it says 16

 

[stangfreak]

3.4 whipple and pump gas dont belong in the same sentence. I don't even run my 2.9 on pump gas.

The 3.4 needs race gas or e85. e85 would be the ideal choice bc the 3.4 whipple, ran at its appropriate boost levels, creates a ton of heat. I dont care what people say that big blowers run cooler. No. e85 will manage the heat better.

 

[MG0h3]

geez I missed the crusher part.

Something isnt right.........

You better take it easy til you figure out whats going on.

 

[GT 11B]

And the surprising thing is it runs 1000x better on 93 than on E85

 

[MG0h3]

Where is your digital gauge getting its ref? Stock MAP? Not entirely positive but I think they only are a 1bar. Maybe someone else can provide info.

Regardless, I would strongly suggest getting a mechanical gauge on there to confirm. You can just borrow or rent one and hook it up behind the dash.

The more info you provide the less things add up. Especially the part about running worse on E85. Only saying this because I dont know youre level of knowledge on the car but youre switching tunes with the handheld between 93 and E, right?

 

[01yellercobra]

Where is your digital gauge getting its ref? Stock MAP? Not entirely positive but I think they only are a 1bar. Maybe someone else can provide info.

That's what my research showed. And that's why I went with the separate boost sensor for my Aeroforce.