cbrock

iTrader: (1)

Title says it all. Fighting hesitation issue, not sure if its too much fuel or a lack of fuel. My aeromotive regulator starts to really up the pressure with boost. Since I'm still on the stock computer awaiting the microtech I'm thinking if it does not raise the pressure 1:1 that I'm causing more bad by having the vac line hooked up to the regulator. Thanks.

RotaryEvolution

iTrader: (30)

i used to think the stockers were rising rate but after some testing recently i believe they only raise pressure to 0"Hg, after that they do not add pressure under boost. that has just been my observation though since the FSM was not clear on this and does not give a test for boost and pressure specs.

cbrock

iTrader: (1)

well I could believe that because you set the fuel pressure or in the stock case you check it by shorting out the coupler and check to make sure it's at about 38psi. When you put it under a vac such as at idle it should lower it to ~28-30 or so.

NZConvertible

There seems to be a lot of confusion over the term "rising-rate". The stock FPR is linear-rate, meaning it keeps a relatively constant pressure differential of 36-37psi between the fuel rail and the manifold (i.e. across the injector). Fuel pressure rises as manifold pressure rises, and the difference between them stays about them same. This happens whether the manifold is in vacuum or boost. With a raising-rate FPR when the manifold is in vacuum it acts just like a linear-rate FPR but in boost the pressure differential does not stay constant, but instead rises with boost, hence the name.

Karack, on a turbo engine if your fuel pressure doesn't rise as boost does, you're on a short road to an engine rebuild. All stock FPR's work this way, including ours. At 8psi boost my fuel pressure reached a bit about 46-47psi, which is a little higher than spec. This is possibly because of my fuel pump rewire, or possible because it was a cheap gauge.

DO NOT disconnect the vac line from the FPR. You will run very lean in boost...

RotaryEvolution

iTrader: (30)

well with the stock TII pump it would hover around 40PSI under load but would drop to around 35PSI near the end of the power band, that pointed to me that the fuel pump could not keep up with the demand. after switching to an FD fuel pump the fuel pressure builds now to 50psi at about 2"Hg and hovers there throughout the power band but does not rise with boost, maybe the regulator is fragged but that was my observation without any test to go by in the FSM i had assumed it was normal for the stock regulator, not that i need much more than 50PSI anyways.

NZConvertible

50psi at 2"Hg? You mean manifold pressure just under atmospheric? That's basically static fuel pressure. Even at FD pump should make barely more than the stock 36-37psi. Fuel pressure should rise smoothly in line with boost. If it doesn't, the fuel pump is not big enough or there's something wrong with the FPR. A leak in the vac line might do that.

cbrock

iTrader: (1)

Okay well plugging the line made the car feel great until it warmed up and then the hesitation was still there. So something else is at work here. I guess I'll have to put the gage on the wiper so I can watch, but I remember it getting up pretty farkin high as soon as I started to roll into boost.

Dcrasta

Cbrock. Have you checked your Coolant temp sensor. Not the one for the gauges, but the one for the ECU. If its not functional, the car will run too rich once warmed up. U need to pull the ECU codes and see if its reporting any faulty sensors.

Also, like NZ conv. says, ALL turbo cars from the factory have a Linear Rate FPR. So at 0-psi boost (Atmospheric) the Fuel pressure should be at the baseline (36-39 seems common for japanese turbo cars). The FUel pressure increase 1 psi per Psi of boost at the manifold. Thats why your vacuum line needs to be connected. THe ECU controls the AFR (Air fuel ratio) by altering the pulse width of the injection squirt. this is calculated based on the fuel pressure staying at the correct 1-1 ratio with boost. [THIS HAS BEEN PERSONALLY CONFIRMED WITH BOOST AND FUEL PRESSURE GAUGES ON THE CAR]

So Pull the error codes for the ECU then let us know because the rest of it is fishing without bait.

cbrock

iTrader: (1)

LOL...I had to laugh at myself yesterday. I was pulling the plugs on the pressure sensor and TPS to see what difference it made and was shocked that there was no check engine light iluminated. Then I found that 88s don't have a CEL. hahahahaha. I guess I assumed that since my 1982 carburated olds 88 had a check engine light that the "advanced" turbocharged injected RX7 would have one too.

I'm going to build the tester today at lunch and pull codes. I'm guessing I've got a bunch since I had unplugged all those yesterday.

I do have to say it smells pig rich at idle. The lack of power I'm getting warmed up (boost stays pegged around 3 and sloooowly climbs up) would seem to say either the engine is all sorts of bogged down or perhaps a failed knock sensor

I will also tap into the computer to monitor the O2 sensor.

Funny I'm spending all this time when I've got a LT12 in my closet. I guess I want to know why it's running this way before I go and rip everything apart. But in the event that it's a failed sensor that I won't need with the stand alone then I'll either track down a used one cheap or just say screw it, drive it as is (weekend/fun car only) and work on the ECU swap this winter.

Dcrasta

Ya maybe the Rx7 is too complex for you. I tell you the more I read your descriptions it sounds like coolant sensor but hey go ahead and rip stuff out, then you will make it even more difficult to fix.

cbrock

iTrader: (1)

Oh I've had the microtech lying around for quite some time. With the new house, other projects..etc the RX became a pet project and never got around to installing it. It also served as a back up for my wagon should it be having a bad time.

If it comes back that the TPS is bad or AFM or something that is $$$ that will just be throw away when I switch over then I won't bother. If it's relatively cheap then I have no problem changing it out in the name of science.

I guess I'm a little too used to my LT1 edit and data logging equipment.

cbrock

iTrader: (1)

Just a quick check when I got home before I took the wagon to the strip. No codes pulled with the motor cold. I pulled the TPS harness and that got me the TPS code, so I know it works.

I will wire a weather pack into the computer harness so I can monitor diagnostic codes, O2 voltage, TPS as well as the knock sensor once the motor is warmed up.

Since I can get it to miss in the driveway in N it should make it a little easier/safer to gather this information.

Dcrasta

Umm, you should be throwing the 02 sensor code until it wams up.

cbrock

iTrader: (1)

Really? Running the car as is with just the diagnostics plugged in, no initial-set jumper or anything?

It's a new bosch O2...not that it means anything, I had the Bosch 02s go bad on my wagon in 5 months : / I guess I'll be curious to watch the O2s on my DVM.

Dcrasta

If its not a heated 3 or 4 wire 02 it has to reach operating temp. The Coolant sensor will be cold also till the car warms up. Its not going to go into closed loop operation until the coolant and 02 sensor warms up. If u look at the temp gauge, you have 3 lines. THe lowest and highest are the operating ranges and the second little line above the cold line is the spot where the 'thermostat' opens (ie 180-closed loop line). So warm the car up to that spot, then pull your codes (with the car in the 'on/start' position.) This would have been the first thing to do before u start ripping things off or turning screws. Personally, I think the car has a bad coolant sensor and there is a code for that if its bad. If its bad, the car will always run in 'warmup mode' (below the line mode) , and with that mode comes the cold start 'choke' enrichment.

drago86

Karak, It sounds like the FD pump is overwhelming the PR, The stock one must be 1:1 or it wouldn't maintain a constant pressure. 1 psi of manifold pressure requires 1psi more fuel pressure to keep everything balanced.


Rising rate fprs are just bandaids that raise fuel pressure 2:1 or more with boost, but fuel pressure isnt linear with fuel dispensed so its a crappy tune.

cbrock

iTrader: (1)

Okay, so I warmed it up and no codes. Drove around in the hesitation spot, returned and still no codes. Car smells very rich. The TPS is also set perfect and checked very close for "dead spots" using an analog meter. I will spray around with starting fluid and see if perhaps I have a leaking block off plate or something. Today I will tap into the ECU to monitor key signals as I drive around: 02, Pressure, knock, IAT and ecu diagnostics. This seems like a classic closed loop control issue. So 02, coolant temp and perhaps IAT seem to be most involved.

Though I have noticed I have a reasonable exhaust leak either from the turbo to downpipe or turbo to manifold. It seems to seal up once it warms up but the odd thing is that boost feels waaaay better cold with the exhaust leak than hot with it sealed LOL. I suspect multiple things at fault here. I know leaks before the 02 are bad, but this hesitation has been around long before this exhaust leak.

Of course I'll double check the plugs, clean them up, check the fuel filter (aeromotive with removable filter element) and check the resistance on my plug wires. I suspect zero improvement.

You pretty much hit the nail on the head...I would LOVE to get the car running tip top before I put in the stand alone. It would cetainly suck to have the same issue before and after and not have any idea whats up...though I would have a much better view of the sensors. At the same time, *if* the stock ECU is having issues, bad ground/cold solder, doesn't like the FMIC, angled AFM...etc, then at some point I have to cut my losses, quit wasting time and just put the stand alone in.

cbrock

iTrader: (1)

okay...*maybe* I have a slight intake manifold leak. I sprayed starter fluid and it seemed to want to cut out every-so-often. So I think a block off is leaking a little bit. I'm going to log the sensors first, collect some information and then reseal all the plates and see if there are any improvements to run condition or sensor readings.

Oh, I did get the o2 to throw a code while warming up.

NZConvertible

Perfectly normal. It'll always do that until the sensor reaches operating temp.

cbrock

iTrader: (1)

yup, that what I suspected. Off for a few moments, code while warming up and then no code once at temp. The search continues.