mmarshall

iTrader: (2)

I have a pullout LS1 from a 2003 vette that I installed in my Factory Five Daytona Coupe. I deleted the egr, evap, rear O2 and converted to DBC. I have a de-screened MAF, Walbro 255 set at 50 psi.

My tuner says he has doubled checked the injectors and they are stock. He says he normally only needs to bump the fuel up 2-3% but on mine he has had to add 20% to the fuel to reach stoich and can't figure out why. So what gives? Any ideas why he is having to go to 20%?

Thanks for any help!

Mike

jimmyblue

iTrader: (11)

That fuel pressure is way low for LS1-normal. The injector flow
rate needs to comprehend the rail pressure. There are some
tuning spreadsheets kicking around which can handle that for
you. If you were (say) to go to a manifold-referenced fuel
pressure regulator at 3 bar, you could gain more consistency
and use nominal ratings (generally; check mfr's rating basis
though).

mmarshall

iTrader: (2)

Jimmy thanks for the reply!

Here is the regulator I am using on a set of "Nasty" fuel rails:
http://www.jegs.com/i/Aeromotive/027/13301/10002/-1

So it looks like we need to set the fuel pressure up to about 58 PSI and try again. I thought the port on that regulator was only for boosted applications. Would hooking up the vac. port help in a non-boosted engine.

The tuner is wondering if the throttle blade is causing turbulence throwing the MAF off because it is mounted right to the TB. Here is the filter setup:

joecar

Several things...

the stock (you said 2003 Corvette) IFR table is configured for 58 psi rail pressure using an un-referenced FPR... if you don't meet those spec's then the IFR has to be edited so that they can be met;

air enters your conical filter and has no chance to become steady flow when it passes the MAF; flow is also skewed to the bottom of the MAF by virtue of the throttle blade being too close after the MAF;

conical filter in the engine bay (behind radiator) is going to pull in hot air, this is a bad thing to happen as it physically promotes knock, and it reduces cylinder air fill which allows timing to advance which together with hot air makes knock worse.

mmarshall

iTrader: (2)

Thanks Joe!

The tuner is starting from scratch on the tune, but I will ask about the IFR tables. He seemed pretty confident he could tune it for the lower pressure as he does LS engines all the time. I may try a new TPS as I am now wondering if the off idle lean problem is due to a bad TPS.

I will try moving the MAF tomorrow and see if cleaning up the airflow helps.

Hot air is not a problem as the Daytona ducts the radiator out of the top of the hood. While not my car, this pic shows the jist of it.

BLK02WS6

iTrader: (2)

Why not go to a speed density tune with a custom operating system and get rid of the MAF? De-screening the MAF makes your problems worse - the screen straightens out airflow some...

I would raise the fuel pressure to 58 and vacuum reference the regulator...

Why would you think it is a TPS? any codes? don't think that is a problem...

mmarshall

iTrader: (2)

TPS because he said it was in the list and then it disappeared. Plugging in a new one to try is fairly easy.

He is not a fan of speed density, but that may become an option.

What will the regulator do when it sees a vacuum source? It raised 1:1 on boost, but not sure about vacuum.

got-a-ls1

iTrader: (12)

i love speed density. the less things that control fueling fighting each other the better i say. I think it does take longer to dial in a nice VE table, but i would never go back to a maf.

also with the regulator hooked to vacuum basically you you just flatline the IFR (injector flow rate) table because as the vacuum in the intake manifold increases ( or as air pressure in the manifold decreases, how ever you want to say it) the regulator reduces pressure. Basically you are canceling out the pressure differential. with the stock setup being 58psi all the time the computer needs to know that the injectors are going to dump more fuel with more vacuum in the intake, because the pressure differential is greater.

also ditch the descreen maf. i have a friend whos lucky he didnt melt a piston because his descreened maf was causing it to run around oh.... 16:1 wide open throttle. i had to add tons of fuel in the tune as well and it still wouldnt run correct... i changed him over to speed density he picked up about 6mph in the 1/8th mile. i think we then took the 12 guage to his old maf hahaha

SSpdDmon

iTrader: (10)

What I would do...

Set tune back to stock (minus adjustments for missing hardware - i.e. EVAP, EGR, etc.)
Run a screened MAF with at least a few inches of straight pipe in front of the screen (use factory MAF values)
Adjust FPR to ~58psi - referenced to manifold vacuum at 0kPa
Flat-line IFR table with the number in the 0kPa cell
Tweak fuel pressure via FPR so that driving fuel trims (not idle) are within a range of +/- ~3%
_____You shouldn't need to exceed 60psi @ 0kPa
_____At idle, the FP should be lower because FP drops as man. vac. increases on a referenced system
Once the above items have been addressed, commence with the remainder of the tune (timing, fueling, etc.)

mmarshall

iTrader: (2)

Stock tune was a 2003 Vette LS1 with an auto trans. In my car with a TKO 500 and converted to DBC we were trying to use a manual tune from a 98 camaro...didn't work. It lost the TPS with that program. We are now trying a program for a 2004 GTO manual trans and hopefully it will see the TPS and be happy.

Without the TPS the MAF and speed density are non-issues.

BLK02WS6

iTrader: (2)

Yeah, 98 tune would definitely be a problem... 04 GTO should work.

mmarshall

iTrader: (2)

Thanks that gives me some hope! What about the 98 tune that made it not work? Should that have been obvious to my tuner?

edcmat-l1

iTrader: (10)

There are quite a few things mentioned that should be glaringly obvious to any experienced tuner.

mmarshall

iTrader: (2)

Update: We finally got the computer to take a tune from a 2002 Firebird with a manual transmission. Car starts well and runs pretty good. Big thing is it is seeing the TPS and responds well to throttle. Now we can tune and get it back on the track.

One problem though. The car now seems to be overheating and has no flow from the water pump. It was flowing before and now it is not. I replaced the t-stat with no luck. If you pour water in the top side of the radiator it flows well out the bottom side so the radiator seems clear. The steam pipes are hooked up to the top of the radiator. I am thinking the next step is to pull the water pump but the tuner says it is rare to have a water pump fail on an LS. So why else would there be no flow???? If it is run with the cap off it starts pushing coolant out instead of allowing it to return back to the motor. Run with the cap on the temp keeps climbing until it overheats and pushes out of the overflow.

Any ideas??? How does a water pump fail while sitting in the shop waiting for a tune?

joecar

Bleed air from the steam tubes.

Check water pump flow by momentarily running with heater hose off (catch the coolant).

mmarshall

iTrader: (2)

Joe the water pump was good. I bled the system the way you recommended and it works great now. Temp stabilizes around 195 at idle and comes down to 185 while driving. It is finally ready for a final tune and then the track.

One issue I am seeing is the idle is erratic. It starts off lean(on the Tech2) and rough and then bumps the fuel up about 30-40% and the idle improves.

Today while driving I noticed the car keeps accelerating for a split second after lifting off the accelerator. Once in a while, after you accelerate and then lift and push the clutch in the car goes to a high idle for a few seconds and then drops back to normal. Ideas???? Is this able to be tuned out?

Thanks everyone for the help!

Mike

.

bayer-z28

iTrader: (14)

^ When you're driving and the throttle hangs for a second is the throttle follower adjustment. Mine seems to do it constantly, even though the tables are stock. The follower is basically your rolling idle (over 0 or 2 mph IIRC.)

And when your fuel bumps up, keep an eye on the TPS or IAC counts. Maybe it's cracking it a hair to account for something and that change in kpa vacuum is referencing the regulator and adding a little bit of fuel pressure = fuel. I've had an open loop hunt for a while I was trying to track down. Gotta fix the VE table first to be sure it's not grabbing another sell adjacent to the idle region.

And thanks for the visual aids..

Slowhawk

iTrader: (12)

Pretty much what Ed said.

bayer-z28

iTrader: (14)

Wait... An 03 Vette wound't have EGR in the first place, wouldn't it? Still check and zero any EGR spark tables? And if he converted to DBC, wouldn't that mean the ETC Scalar would have to be zerod? Adjust for new IAC tables? Wouldn't you almost have to rebuild the idle airflow tables for a different TB?

01ssreda4

iTrader: (96)

And you helped about as much as he did.