Suncoast Rod Shop

Got a question that I hope members on here will be able to give some insight or advice on why my customers car is not making close to the horsepower/torque numbers we were hoping for on this rebuild.

Heres the lowdown on the motor/car in question - 95' Impala SS with 427 LSX built by Nelson Competition twin Precision 62/65 turbos. Tial wastegates (not sure of the exact size??) MagnaFuel Pro Tuner 750 #4303 fuel pump. -10 fuel lines (both send & return) Injector Dynamics ID1300 injectors.

Originally the car came to me by another shop that had no business building a car of this caliber. The headers/exhaust were an abomination (I won't get into everything that was wrong about them) It had an external Weldon pump (good for 750hp only) -10 fuel line into a Aeromotive regulator that was regulating the pressure before it got to the stock fuel rails. The regulator was bolted to the driver inner fender right behind the headlights/ radiator core support. Coming out of the regulator was roughly 4 feet of -6 line into the stock fuel rails. 70lb fuel injectors. Initially I went to have the car dyno tuned and 1st pass on the dyno it put down 844rwhp on 16lbs of boost and the fuel pressure was dropping. The tuner bumped the fuel pressure up to 60psi- round II put down 799rwhp and the fuel pressure dropped again so they said until you fix the fuel delivery no sense in me trying to tune this thing.

Long story short the motor got toasted sometime later as the customer didn't upgrade the fuel delivery and distorted the pistons, burnt up rings, etc...
So last year it came to me to redue everything. The motor got pulled back out- re freshened back up by Nelson Competition. New pistons (same compression ratio as before either 8:5.1 or 9:0.1 I don't remember what they told me) basically everything internal of the motor stayed the same.
I fabricated new 1-7/8" 321s.s. headers, upgraded the fuel delivery and plumbed for more than the motor will ever make. Redid all the hot/cold side of the turbo piping, same waste gates, blow off valve, innercooler, transmission, rims, etc....

Finally got to see it run on the dyno this past weekend and everyone including myself figured it would lay down close to 1000rwhp and so far all it could muster was a disappointing 650rwhp. with 14lbs. of boost. According to the tuner the fuel & air consumption that its doing - the math equates to roughly 1150hp at the motor but we can't figure out why the numbers are so dismal??

Im not a tuner - just a really great (albeit dumb sometimes) fabricator. According to the tech at Precision Turbos when the turbos were sent back for repair I was told these particular turbos are good for roughly 700hp each. So how is it that in such sad engineering state as it was before I redid everything it layed a mid 800hp run with no tuning and after reduing/ re - engineering everything correctly it falls on its face??

Any ideas, and or suggestions?

JoeNova

Ouch. Thats less power than my stock 5.3 made.

What trans? What fuel? What tires?
My first trip to the dyno (Dyno Dynamics, reads 15% low), I couldn't make more than 500 to the wheels. I first hit 500 wheel with 50% injector duty cycle, at 14 PSI. Turned it up to 20 PSI. 93% IDC, still only 500 wheel. Turns out, drag radials on this dyno aren't the best idea.

You could also be blowing through the converter if its an auto.

Or the cam timing could be off. Lots of reasons for poor dyno numbers.

silversweetZ

iTrader: (11)

When you say upgraded the fuel delivery system, what did you go with for injectors? Almost sounds like low fuel pressure/low timing.

Suncoast Rod Shop

trans is a 4L80E - same transmission/ convertor that was in it on the 1st 844hp pass along with the same 22" diameter rims. I initially thought the transmission was slipping but if it was the numbers would get worse with each pull if that were the case - or one would think??

Injectors are Injector Dynamics ID1300 (I spoke to tech at Injector Dynamics- gave all the information on the motor, turbos, setup, etc..)

Fuel pressure is at 45psi ( I think??) I forgot to ask the tuner - however I would expect him to check that. The tuner Im using is a noted tuner in my area and is familiar with high horsepower (1000+) forced induction setups.

Suncoast Rod Shop

I had posted on here last year of the build in progress showing photos of the headers and all the work done. I think the thread was 95' Impala ss twin turbo build.

here's the link to that build thread if you care to see the setup
https://ls1tech.com/forums/forced-in...rbo-build.html

JoeNova

1:1 regulator with boost line hooked up?

Suncoast Rod Shop

Yes as far as I remember but I will double check again tomorrow when I stop back by the tuners shop

93hatch

iTrader: (9)

collapsed flex section in exhaust?

Suncoast Rod Shop

Which flex section are you referring to? The ones underneath the car?? The flex section on the exhaust I used are by Vibrant Performance and supposedly are for turbo applications.

aireegory

I had posted on here last year of the build in progress showing photos of the headers and all the work done

alocker

iTrader: (10)

Post up the dyno graph and AFR curve.

Did you boost leak test it before the dyno? Is it the same dyno?

EarlyZ28!

iTrader: (2)

Dern all that money for 650 would b a lil discouragin

vinceI

iTrader: (5)

Post up dyno sheet. Any idea on converter/transmission slip? Could it have been spinning the tires on the dyno?

forcd ind

iTrader: (7)

If the dyno said it was using enough fuel and air for more power, then was the engine making more power now and you were looking at driveline or tire slippage or something else-an engine dyno would eliminate some of that
Or were the AFR's pig rich? prob need to look at the dyno readings, data logs, see what jumps out

408GT

iTrader: (2)

Reading through it, my first thoughts were trans/converter. Can you calculate the slip and verify that those aren't the issue?

Suncoast Rod Shop

I will post the dyno graph and AFR curve later this evening when I get a chance to stop by there this afternoon. If memory serves me correct I want to say it was around 11:1

I did not boost leak test it before the dyno other than checking the innercooler for leaks as I modified the tanks from what it was before to fit the area it was relocated to. All the pressure piping running from the turbos - innercooler - towards the throttle body have V band/ Marmon clamps, minus the bump hose at the throttle body which at around the last few pulls (which I was not present for) and around 14psi of boost it was blowing the bump hose at the throttle body. I will be stopping by to take a look at the piping at the throttle body to see what needs to be done to correct it today.

Suncoast Rod Shop

Yes a lot of money spend correcting the original design/setup, very discouraging right now.

Suncoast Rod Shop

That was my thought too on transmission/converter slip but when I posed that question to my tuner his thoughts were if the trans was slipping the numbers would progressively get worse - which they were not.

It is possible the tires are spinning- I will bring that up to him today.

408GT

iTrader: (2)

It could be making enough power now that it's blowing through the converter.

gtfoxy

My first thought.

Beyond that yank the motor & strap in on the dyno to take out a lot of variables & to see what it really does.