bripab007

Least. Coherent. Post. Ever, ever.

magnamx-5

iTrader: (7)

20-25 psi of FP will not work dude. he needs to tighten the afm and then maybe lessen his FP to stock levels but this is hard since the 255 flows a **** ton of fuel i bought a adjustable fpr for mine and it flowed less than my stocker no matter what i did to it so i went back to stock and 5-10 psi higher idle fuel pressure. he could tweak his ait to show a hotter engine bay enviroment and trim fuel up top that way as well.

Hammerhead

That's absolutely right! I bought this setup from 93mimi. He is a friend of mine and I gave him a call so he could provide me some sage advice. Basically, he said I was introducing even higher fuel pressures with the 255HP that the stock pressures I was already having trouble with. I was thinking backwards and that I was having fuels (or pressure) starvation at the top end. He said that I would need to lean it out further and reduce the fuel pressure.

Don't be too critical of greddymx5. I think its a language issue between American English and the Netherlands English. Nonetheless, he is right. 93mimi told me the same thing that greddymx5 is saying here. I can even bypass the stock FPR to verify this. Furthermore, assuming the stock FPR is functioning properly, I could add an adjusting valve to adjust fuel pressure (which is what I assume an AFPR does).

Anyways, I was able to resolve this issue by leaning out the RX-7 AFM another tick and regapping my plugs down to .032 from .039. The car is plenty fast and torquey now and NO hesitation from 4500 - 5500 as before.

This makes sense. 93mimi also told me to watch the EGT carefully. At a good steady pace on the highway, I should expect to be running a good, hot 1400 - 1500 degrees. This would ensure a good, efficient burn-off of available fuel. When jumping on the throttle and introducing more fuel, I should cool a little bit.

greddymx5

iTrader: (1)

As i stated above i don't know what the minimum fuel injector pressure is to get it to work properly.... The 20-25 psi is a simple 1/2 of normal fp as the injectors are 2x as big as oem.
Of course you can fool the ecu to to give less fuel through the afm.

bypassing the oem fpr is done frequently with good results.
If you need less than oem fp because of bigger injectors just bypas the regulator and insert a valve in the bypass. This way you can control the fp @ the fuel rail.
The afpr will increase fp @ boost levels so nothing is wrong.

bripab007

That doesn't sound right at all. You should see the highest EGTs at sustained full-throttle/max-boost.

Hammerhead

You should see an initial drop in EGTs, but it would not be sustained. IIRC, you would see this if it is running too rich and the fuel in introduced and doesn't burn efficiently. The effect is it cools the EGT...not by hundreds, but by 25 - 50 degrees.

I need to do more research, so I'm not talking outta my @ss.

samnavy

iTrader: (7)

I have another idea wrt your bouncing idle. I've got it too (BAD) and my AF at idle is fine.

When was the last time you adjusted your actual idle speed?
http://www.miata.net/garage/ignition.html

It's possible you could have a sticky IAC.
http://forum.miata.net/vb/showthread...ight=air+valve

4sfed5

Dont want to be a hater BUT........

This is soooooo funny....your running a 255 walbro which is known for overpowering the stock FPR AND you have 440's installed....ON A STOCK ECU

just another classic case of "it runs fine BUT it doesnt idle properly and gets crap mileage (17MPG )and has hesitation etc etc"...THATS NOT RUNNING FINE THATS ****!

Get rid of the 255 and fit a 190LPH and then sort out your fueling properly. id say your hesitation is actually a rich condition...the stock ecu g0es way rich above 5000, and coupled with the 440's id say your drowning it in fuel.

The stock ecu uses fixed rate acceleration enrichment so the bigger injector you use the more fuel it dumps in when the throttle is cracked.doubling the injector size means double the fuel going in for the same amount of airflow which is going to give you hesitation problems.

your never going to get a half decent fuel curve with a stock ecu and no piggy back especially at that sort of HP and injector size.Anything you do with this setup is going to be a comprimise, and youll have to tune for the worst case in terms of knock, so everywhere else in the rev band is missing out on HP.

with your setup and HP id be looking at a megasquirt to sort it out.

THIS THREAD IS A TESTAMENT TO HOW TOLERANT THE MIATA ENGINE REALLY IS!

Joe Perez

iTrader: (8)

+10 FTW on that one.

I ran air-cooled VWs for a long time, and those poor little things would suck down an exhaust valve or spin a rod bearing if you so much as spoke the words "Forced Induction" too loudly in their direction. The '71 and later 1600s weren't quite as bad, but you'd never even consider throwing 18PSI at one without spending at least $15,000 on just the case, crank, rods and heads. At that point, the only part left in the engine that said "Erbauen in Deutschland" was the dipstick. And you just accepted the fact that doing a bottom-end rebuild every other oil change was the way things were.

I hear so many conversations where people say "I'm running 42 PSI with no intercooler at 30 degrees BTDC base timing, and my gas tank is filled with cat urine and cheap whiskey" and I have to wonder just how loud a stereo you need to mask that kind of pinging. And yet for some reason the freeways are not littered with pieces of Miata engine case and rod.

Ours is truly a robust powerplant.

Hammerhead

Dude! Be kind! Actually, I got the hesitation resolved at WOT and I have no ping. I am idling pretty well, with an occassional hunting, but not every time I go to idle. I AM getting crappy fuel mileage (17 MPG at boost), but the car runs like a scalded dog! When you get into boost, its not like a push in the back...it's like HOLY SH|T! And your hanging on for dear life! I romped on an M-Roadster last night (up to about 95 MPH, where his gearing took over) and just lead a new Mustang Cobra today.

Admittedly, the car IS a compromise. 93mimi had the car at the same or better performance levels AND 36 MPG highway. What I want to do is understand how to do this with stock components. I have three more motors in the garage and am looking to build a new motor for the other Miata for a bigger turbo setup with a complete stand-alone ECU. What is so much fun about this car, other than the *****-to-the-walls performance is that it is the ANOMALY. You shouldn't be able to do this withi this setup. I'm sure that someday, I may kill this motor, but I will have fun tinkering until then and then slip another motor in the bay.

As far as a forgiving motor, don't forget this IS a turbo motor (323GTX). It has forged rods from the factory. Albeit not for this much boost, but it IS a strong motor. That can't be said for the 1.8 and later powerplants.

magnamx-5

iTrader: (7)

actualy it can. so while 93mimi and Andy, and a few others including me are anomalies of the stock ecu macking big power, the 1.8 is every bit as strong as the 1.6.

rotaryjunky

iTrader: (3)

The stock ecu must really go rich at 5k because I just confirmed tonight that my vortech wasn't doing anything! I was running 6/7 psi on a stock fuel system (just the o2 clamp probably saved me!). I have done a compression check this winter and its still perfect. I didn't drive it very much with the turbo, thankfully. It hesitated (duh) until 5k, then it pulled well. It actually ran pretty well at partial throttle over all rpms. I finally got a pressure/vacuum pump and put 10psi to the fmu with no rise in fuel pressure. Learned my lesson.

magnamx-5

iTrader: (7)

WTF ouch

rotaryjunky

iTrader: (3)

Next time, it will be:

1. Fuel pressure gauge
2. Wideband
3. Fully tested FMU
4. All that other turbo ****