fuzzyjk

iTrader: (4)

94 Z28, Fresh rebuilt 355 LT1, 227 Crane Cam, LE1 Heads, 1.6RR, Kooks headers, full catless Borla exhaust with cut outs, Vortech supercharger with 6.5Lbs pulley, 42lbs injectors, through a 3200 Edge stall, Line locks, Fireball, full suspension....blah blah blah. Made 302hp 422tq. Dyno operator noticed the fuel presure was dropping off to 35 and recomeended a new 255 pump be installed. Any reason why the Hp and the Tq are so far apart. Something seems to be a miss. I was thinking the HP/Tq would be in the low 400 range. Any suggestions...advise?

BOLO

iTrader: (40)

Dyno tuner just answered your question. It going to lose hp with low fuel pressure.

fuzzyjk

iTrader: (4)

But still have good TQ?

SS RRR

iTrader: (2)

FI applications can produce massive torque. In some case, moreso than horsepower. Probably would be a good idea to post up the graph? Do you know what your air/fuel was during your pulls?

fuzzyjk

iTrader: (4)

Ok I will get the sheets from the shop tomorrow and post. I was not present for the runs. He said at cruise it was around 12-1 and a full stride it was 15-1 and they shut it down when it had one spike to 17-1. I am running a Walbo 225 now. Looking up online... AEM and Areomotive stand out as being good options. The engine alone should put out 325whp with anther 100whp coming the way of FI. Seems like more then a fuel pump issue. Could it be a faulty injector? At my hp level, the fuel rails should offer plenty of flow.

LLLosingit

iTrader: (4)

HP would likely have continued to climb if they wouldn't have had to abort the pull, So that would explain the difference. You got peak torque numbers but not peak HP numbers.

BALLSS

IDK if the 255 in tank is enough "pump" by itself for the FI w/42 lb injectors

My friends 95 with a Vortec is also running a external FP. Also has 42 inj

fuzzyjk

iTrader: (4)

What is your friend making for numbers? I would be happy with 420/420. Very happy in fact.

fuzzyjk

iTrader: (4)

Here is the project car.

handyandy

The consensus online seems to be that a 255 lph fuel pump will support up to 475-500 whp, so that would seem to be sufficient for your setup.

As for having a bad injector, I know my tuner can "turn off" specific cylinders in his software. He used this on my car to try and troubleshoot an underpower condition (although in my case it didn't show anything, ended up being a clogged muffler). If each cylinder is working correctly then you should see a noticeable difference when turning it off. If you see no difference then it would indicate an issue with that one.

Shownomercy

iTrader: (1)

Thats a great way to make piston soup.

Why not fix the issues you have and then chase HP numbers.

I would run two walbro 255s in tank and one triggered off when you get into boost.

fuzzyjk

iTrader: (4)

Piston soup, that made me laugh but you are right. They drove it on the Dyno as part of the break in and once it seemed to be good they tested to see output. We obviously will not Dyno again until we find the cause and at minimum swap out filters and pump. Could it be anything else other than fuel pump?

fuzzyjk

iTrader: (4)

Here are the graphs. The Dyno operator shut down at 4000rpm due to lack of fuel.

BALLSS

his is a stock LT1 with just Vortec, 42 inj and a tune. IDK what dyno is, he never dyno the car. Vortec installed it and tuned the car as they are local.

he has a stock in tank pump + the external one Vortec added

KW Baraka

iTrader: (7)

Typically with mild cams, the LT1/4 engine reach peak torque below 4000 RPMs.....which was a good way before the engine got to it's peak HP.

Get the fuel issues sorted out and your peak HP should be around 350 at the wheels.

KW

fuzzyjk

iTrader: (4)

And that is why I thing something else is going on. 350 at the wheels for a h/c boosted car is very low. Should be 325whp with mods na. Or am I mistaken?

KW Baraka

iTrader: (7)

OK......I missed that part.

In that case, even your torque numbers are a bit low.

But it's nothing that a 255LB pump and a good dyno and street tune can't cure.

KW

fuzzyjk

iTrader: (4)

I like that answer. Thank you. I would like to see at least Ls3 stock numbers 380–390whp.

I have other decent hp cars but this one has been a long project and it was my ride to my wedding 20 years ago. I want to do period correct mods and get as much as I can. I know it is no LS7.

Puck

iTrader: (17)

No point in any questions until you get the FP replaced. That is dangerously lean for a boosted setup.

New FP - I would go dual 255s or a 340+bulkhead upgrade at minimum - then finish the dyno tune to see where you are.

fuzzyjk

iTrader: (4)

Has a brand new fuel pump in there now that came with the kit. Must be defective.