I went to get dyno tuned today

The guy had never used a PFC before but he's tuned FDs before, so I gave him the instructions a week in advance and set up the appointment.

With my heavy *** rims at 11 psi on a GT3540R turbo I pulled 290 hp. At 13 pounds I pulled 303, but he said the injectors were maxing out at that point and it was starting to run dangerously lean.

I'm thinking to myself, that's not right - those injectors should be good for 450 horsepower, right? Does this guy just not know how to tune? (he's got the world's fastest 3000GT VR-4 and a very reputable shop . . . )

Or am I wrong - do I need 1600cc injectors and a fuel pressure regulator? This is like $600 (which I have to spend since my suspension checked out - the spring rates are just too high, the rest of it is fine).

I have a Supra fuel pump and the 1250cc secondaries, 550cc primaries, Power FC, AVC-R, 3mm seals, full rebuild, GT3540R, GReddy stock mount intercooler, etc etc.

 

I run 550/1200 and made 347RWHP at 94F air temp with stock non-seq turbos at 15psi and almost stock ports with about 83% inj duty.

Made 315RWHP at 12 psi.

Somthing is not wright. I think your AFRs are stinking rich!

 

Chuck,

What are your AFR's are your targeting under WOT & Max Boost?

 

What shoudl the AFRs be ?

He seemed to have them at 14-12ish

 

At 12psi boost (P17) mine are set for 11.6AFR.

For 14-15psi boost (P18) mine are set for 11.3AFR.
Some may say these are a little lean, but my complete setup makes it safe.
Plus I have been tuning it for three years in all weather conditions and with seasonal fuel changes.

On the day I ran 347RWHP at 15psi boost with 94F shop air temp, my intake air temp was only 104F due to my BLITZ FMIC, M2 large radiator, home made nose ducting, 550/1200 injectors with improved Nippo fuel pump , etc.

 

are you using a fuel pressure regulator?

I'm on 1250ccs and they say I'm maxing out at around 13 psi, which is weird.

I think he was running more like 12-13, which I guess is too lean, and still maxing out.

Maybe its a clogged up fuel filter?

 

With 4x 850 cc injectors, I am running 11.2-11.4 A/f at 10 psi on a gt40r. Thats with a maximum of 75-80% duty cycle. 80% is when I hit a little over 10 lbs.

 

I am also running a 20b fuel pump.

 

so I checked the PFC to see if it was set up for the injectors, and it was . . . . . . . 550/1250

 

I am running a stock Mazda FPR and stock pressure:
28-32 at idle, 36-38 0 boost/vacuum. At 12PSI boost = 50PSI fuel.

 

I think mine are pretty rich compared to your AFR's. Mine are in the 10.6 to 11.4 range. I think I'm leaving alot on the table.

 

do you think an FPR might help?

 

I have my boost gauge and fuel pressure gauge mounted side by side where the dash center speaker was. That way I can compare both at the same time.

A fuel pressure gauge is a must for initial tuning of a fuel system. It can help identify fuel delivery problems such as low or high presures.

 

well you have to compare apples and apples. all cars are different and a single turbo is going to flow more than twins. i agree that you should be able to get more fuel with your setup. changing the fuel filter is never a bad idea. as chuck suggested a fuel pressure gauge would also be a good idea. i have 850s bored out to 1300s by rc engineering. i run an apex rx6 with around 15-17psi and the same fuel pump as you and I am <10.5 at WOT. Do you have a datalogit? It may be that he cannot compensate enough with the injector map so that you need alterations to the base map, or you need to go through the PIM %. If this guy is not familiar with the PFC, I think the best advice is to find a tuner that is, world's fastest 3000gt or not. At least he's credible enough to stop pushing the envelope when your afr's were lean. if you don't have a datalogit then you should find someone who does so that you can fully program your PFC.

 

those injectors are good for ~420rwhp MAXED OUT with stock FPR

Theres something wrong. I doubt the fuel filter could be that clogged, I think the guy doesn't know how to tune. You'de have to tune it for 9a/f to use that much fuel up.

are you sure the 1200s you bought are not really stock 850s?

 

You should be able to do about 340 whp at only 70% duty cycle with 550/1250cc, 43 psi differential fuel pressure @ 12:1 AFR @ ~ 1 bar boost (according to my numbers, but don't put money on it )

 

You need to check your fuel pressure. It sounds like your loosing pressure. Might check the vac line that goes to the fpr and make sure its on a good pressure nipple and that there are no cracks in the line.

Stephen

 

thanks a lot guys
I'm going to change the fuel filter and check the lines, and then get a pressure gauge to see if that's the problem

if it isn't then the guy obviously doesn't know how to tune, and I'll need to find someone who does.

 

so do you have a datalogit or not?

 

no but my shop does
I don't know if its worth another $300 to go back to them yet, until I do everything I can do on my own

 

oh, another fuel system issue

I have the anti-knock mod from KDRotary that shuts power to the engine when it detects pinging.

Whenever the gas tank is full, its fine, but as soon as it drops below 3/4 I can't really exceed 5000 rpm without the engine shutting off, like its starving for fuel . . .

 

SPOautos is coprrect, check fuel pressure first. I dont know why most dynos dont or wont
invest in a fuel pressure sensor to measure with. We allways graph boost to fuel pressure
and it better follow within a pound or two thru complete run, or dyno session is over. Allso
those injectors should be for that boost level, you need to find a qualified PFC tuner, and a
better dyno center with the right tools, or you will be buying a new motor. Regarding your gas tank level, 3rd gens slosh so bad at 2/3 tank and below they suck air. wWhen we are running big singles at high boost25-35psi, we never let the tank get below 1/2 or the motor starts to suck up air ballsw. Ralph

 

do they make replacement fuel tanks?

 

you need a better tuner. i think demetrios or someone like that is down by you in the MD area. don't waste your money taking it back to the first guy.

 

We sump the factory tank, summit sump $60 then wel in with outside pumps. Ralph.