this one is for twin turbo guys

[jwhisl]

I've got a friend that just installed a 50mm twin turbo kit on a 351. We went down to the dyno yesterday to get it tuned. The first thing the tuner noticed was a miss at higher rpms. He made a base tune so the fuel was ok. The thing is it made less horsepower than it did before the turbos. Heres what I know about the engine: it has edelbrock heads, roller rockers, e303 cam, gt40 tubular with minor port work, and 60lb injectors. I also know hes running a stock gt maf. Car is making less than 200hp at 3400 rpm at 10 to 15lbs of boost. Any ideas?

Edit: we never revved it higher than 3400 because of the miss

 

[RichV]

It could be a mountain of things. The combo sounds legit, but it could be anything from tuning, fuel, turbo install, exhaust, ECU, whatever.

I would probably start with wastegates and BPV or BOV. Make sure the cold and hot air are going where they should. If he's running a single MAF it's setup for a blow-thru and IIRC you need a special MAF for that, but I have no real experience with that. A buddy with a similar setup and a single turbo was around 300hp/400+ft/lbs at that RPM.

 

[ttocs]

Last time I went too the dyno after my HCI swap I had a problem with my ignition. I ended up replacing the dist cap/rotor and then the coil and it fixed it but the tuner told me to start there.

 

[rz5.0]

What plugs is he running. Is it stock ignition.. so there was no issue with the car prior to the install.. what maf are you using..

 

[jwhisl]

Stock distributor. I dont know what plugs hes running. Stock maf on the exit tube from the intercooler. I cant remember but I think hes running msd coil and box. No exhaust on the car yet

 

[ttocs]

not eve sure why you would limit the air intake ability of it with the stock maf myself.

 

[rz5.0]

For turbo you guys need a blow thru... it's better suited for application.. I would also bypass the msd box for now.

 

[jwhisl]

For turbo you guys need a blow thru... it's better suited for application.. I would also bypass the msd box for now.

I didn't build the car. My guess would be trying to keep cost down but it looks like the general consensus is the maf or the ignition?

 

[ttocs]

Saving money on a twin install - interesting. The stock maf is where I would start. Did he save cash and keep the stock injectors then too?

 

[rz5.0]

More than likely

 

[jwhisl]

He got 60lb injectors. The turbo kit was a cheaper kit though. There was a bit of modifications that needed to be made to the piping for it all to fit. Ill tell him to get a different maf and go form there

 

[ttocs]

replacing the maf will more then likely require another trip to your tuner although I am sure you were expecting or hoping to go back.

 

[rz5.0]

Find out for sure what maf. How it's routed. I would also bypass the msd box. Check spark plugs.. was there no issue before the install..

 

[jwhisl]

Before the install he made like 297 at the wheels. Everything seemed fine in fact he ran a 12.70 1/4

 

[Addermk2]

sounds like he should give up on the hobby...

 

[rz5.0]

That's weak for 351.. he should of invested the turbo money else were and made more power N/A

 

[rw95gt]

My guess is the tuner left all the timing out to keep it safe. No timing will give you no power. You can't compare before and after numbers when the car isn't tuned correctly and the pull stopped at 3400 rpm. I'm sure he didn't run 12s shifting at 3400rpm. I wouldn't worry over synopsis numbers so much. Focus on fixing the miss fire issue so you can get some timing in the car. Also I agree with others saying the stock maf is prob not going to work correctly with his setup. I don't see why and how it could work with a blow through set up or 60lb injectors. What brand kit? What is the A/R of the turbos? What size exhaust housing?
Sent from my SAMSUNG-SGH-I727 using Tapatalk 2

 

[ivan12]

I'd start at the cheapest fix, what plugs and where are they gapped.

 

[2002BLGT]

you cannot run a stock MAF on that setup , and as stated it needs to be blow thru setup , lord only knows what the real problem is but need to check everything , spark plugs , wires , fuel pressure etc. , who was the tuner ? What did the tuner suggest doing ?

 

[shoua50]

Did u say "stock maf on the exit tube of the intercooler" and 60lb injectors. There's your problem. The stock maf needs to go on intake side of turbos. Using the stock maf as a blow thru sensor will not work, that's y it won't rev. Need to get an actual blow thru sensor that's calibrated to injector size if u r gonna put the sensor on the exit tube of the intercooler.