I was reading my 88' service manual, I like to do that sometimes, and i was reading how the cold start injector works. I was thinking why couldnt you use a boost referance switch to switch ground at a certain boost point to inject more fuel, That way you could use stock injectors but run more boost. Also i read that the egr vacuum control assembly has a filter on the end, your suppost to change at 30,000 miles its called EVRV filter has anybody else heard of this filter.

Sounds like a plan, where do you get a boost referenced switch?

Tests that we did a while ago with a wideband O 2 sensor confirmed that the stock #15 2.8L injectors are capable of supporting 9-10 psi of boost IF the programming is changed to enhance the main fueling and power enrichment tables accordingly. You are not putting more boost in any stock 2.8L without blowing one of the stock cast pistons so more fuel is not required. The only thing you might do with the cold start injector is turn it completly on or completely off IMO not a good way to control any type of fueling.

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87GT 3.4 Turbo- 0-60 5.2 seconds
2006 3800SC Series III swap in progress
Engine Controls, PCM goodies,
re-programming & odd electronics stuff
" I'M ON THE LOOSE WITHOUT THE JUICE "

that is a classic trick.
the fun part is controlling it.

quote Originally posted by projectformula: I was reading my 88' service manual, I like to do that sometimes, and i was reading how the cold start injector works. I was thinking why couldnt you use a boost referance switch to switch ground at a certain boost point to inject more fuel, That way you could use stock injectors but run more boost. Also i read that the egr vacuum control assembly has a filter on the end, your suppost to change at 30,000 miles its called EVRV filter has anybody else heard of this filter.

Can you please elaborate on your plan with the cold start injector. First off, I can't even find where it is located. thanks

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1986 GT Fiero Owner & Enthusiast

quote Originally posted by chrismclubm: Can you please elaborate on your plan with the cold start injector. First off, I can't even find where it is located. thanks

it is on the back side of the intake minfold, near the distributer. there is a small 1/8" metal fuel line coming out of the fuel rail, if you follow it, it goes to the cold start injector.

I was thinking of doing this as well, so I did a search and found this thread.

Im having lean problems at 10-11 psi. I think the CSI set to spray at 10psi will help me out, but I just have one minor concern. That is, with cylinders 1 & 2 being furthest from the CSI, will they be getting the fuel that they need?

The fuel distribution via the cold start injection system is not precise at all, so there's no real way to guarantee that the cylinders get equal amounts of fuel. Plus, the injector is an all or nothing design, there's no way to alter its flow rate. At WOT there's only fixed fuel tables so there's no way to adjust fuel trim using the ECM.

All in all it sounds like a bad idea to me.

Get 3.4 injectors, they flow more and bolt right in.

JazzMan

I have new 19lb injectors, and they are too rich below WOT and give bad driveability issues. They were taken back out. The 17lb injectors from the 3.4 may be better with driveability, but I dont feel like spending another $200 just to put those on a shelf either.

I suppose if the CSI runs rich, you can resist the power supply voltage to decrease the flow. Hell, you could even wire it in with a rheostat so you DO have adjustability, but now we're starting to get on the border line of half-assing things. Its just that this idea is so tempting to try as it would only cost $20 for the switch, and I can use the instrument light dimmer as the rheostat. I never dim my gauge lights anyway.

The only other thing I can think of is a rising rate FPR with boost reference, and a rate ratio of 1:1.

[This message has been edited by AutoTech (edited 02-18-2008).]

quote Originally posted by AutoTech: The only other thing I can think of is a rising rate FPR with boost reference, and a rate ratio of 1:1.

The V6 FPR already has a 1:1 boost reference. The vacuum line that reduces fuel pressure during idle and other high vacuum situations will supply manifold pressure to the back side of the diaphragm resulting in an increase in fuel pressure of 1psi per pound of boost. You would want at least a 2:1 rate to be meaningful, but if you're going to spend the money on a FPR, why not get a new PROM calibrated for the 19#'s?

EDIT to add:

The CSI is a solenoid type valve, so a rheostat on the voltage supply line would not alter the fuel delivery until the voltage got too low, then the injector would close. If it were a pulse width modulated injector you could modify the frequency, but it would be very complex to retrofit that type of injector to the CSI port. If you really want to use an extra injector, installing it into the upper plenum, just behind the throttle plate would be the best bet for equal fuel delivery.

[This message has been edited by FieroJimmy (edited 02-18-2008).]

quote Originally posted by FieroJimmy: The V6 FPR already has a 1:1 boost reference.

Right, and wouldnt adding the MSD-2222 FPR on the return line essentially make the system as a whole, 2:1?

quote The CSI is a solenoid type valve, so a rheostat on the voltage supply line would not alter the fuel delivery until the voltage got too low, then the injector would close.

A solenoid is basically an electromagnet, am I correct? So in this sense, why wouldnt weakening the magnetic field vary the "pulling" force to the valve?

quote why not get a new PROM calibrated for the 19#'s?

I tried this with DarthFiero (Sinister Performance). I had about 5 chips made in total, and the car always ran like garbage, it didnt even want to idle. I gave him all the information he wanted / needed, but he could never get the car to run, even admited that he doesnt understand the idle issue. I just gave up on it, the chip that came with the car works beautifully, Im just running out of fuel up top.

quote Originally posted by AutoTech: Right, and wouldnt adding the MSD-2222 FPR on the return line essentially make the system as a whole, 2:1?

No, Both would be set at a static 45psi, then when boost was applied they would each go up equally 46, 47, etc.

quote A solenoid is basically an electromagnet, am I correct? So in this sense, why wouldnt weakening the magnetic field vary the "pulling" force to the valve?

Well, I was going to answer this, but between the time I loaded the message, and the time I hit reply, you posted again. At least it was a spare...

quote I tried this with DarthFiero (Sinister Performance). I had about 5 chips made in total, and the car always ran like garbage, it didnt even want to idle. I gave him all the information he wanted / needed, but he could never get the car to run, even admited that he doesnt understand the idle issue. I just gave up on it, the chip that came with the car works beautifully, Im just running out of fuel up top.

Do you have the equipment to read the PROM and send someone a copy of your current one as a starting point, or was Darth trying to recreate the whole thing from scratch? If one were to take what you've already got, it shouldn't be too hard to scale the injector tables for larger injectors, unless they were trying to be operated below their minimum (the shortest duty cycle the injector driver in the ECM can handle). It's usually not an issue until you get into 60#+ injectors on relatively small engines, though.

If you put in the larger injectors with an adjustable FPR you could dial some of the extra fuel out by lowering the set pressure. I wouldn't want to go below about 25psi at idle, or the spray pattern of the injectors would start to deteriorate. If you were to do this you couldn't pull all the extra flow out at idle, or it would negate the benefit under boost, too.

Ok, lets go back to the stock regulator as I've been doing a little research, and I'm starting to get confused here.

You say that the stock regulator is in fact a rising rate regulator, set at 1:1. However, the information Im seeing is telling me the opposite, that it reads vacuum - 0psi only, and does not use boost as reference. It will only raise fuel pressure until atmospheric pressure is reached. Once boost is introduced, the fuel pressure is now being pushed back by intake pressure, and in turn actually decreasing the fuel pressure.

Everywhere I look says that the FMU and RR regs "are designed specifically to add fuel to modified EFI engines (turbo, supercharger, ect)" Dont most EFI systems have a similar regulator as the Fiero?

Quoted from Cartech - "The rising rate regulators fit into the fuel system after the stock regulator, and in series with it. The regulator becomes the last item before the fuel returns to the tank. Do not remove the stock regulator, as it still controls the fuel flow under most manifold vacuum conditions. "

So.....yeah

[This message has been edited by AutoTech (edited 02-19-2008).]

quote Originally posted by AutoTech: Ok, lets go back to the stock regulator as I've been doing a little research, and I'm starting to get confused here.

The stock regulator has a spring that holds a pintle type valve shut, when fuel pressure exceeds the pressure the spring is holding the pintle with, the pintle rises and allows excess fuel to return to the tank. Between the spring and the fuel there is a rubber diaphragm sealing the two apart. The side of the diaphragm away from the fuel is behind the black canister on the fuel rail. The canister has a vacuum port. The vacuum assists the fuel pressure in overcoming the spring pressure, lowering fuel pressure under vacuum conditions. Now it's not intended to raise fuel pressure under boost, but the manifold pressure (or lack there of; i.e. vacuum) affects the effective spring rate. 20 inches of vacuum (about 10psi below atmospheric pressure) reduces fuel pressure by about 10 psi (45psi key on, engine off; 35psi engine idling). Therefore when the manifold is under boost, the extra 10 psi in the manifold (and all the vacuum hoses, etc.)will be assisting the spring, causing the effective spring rate to rise.

The thing to remember is anywhere trying to sell something has a good reason to say that their product is superior to what you already have. Also, when was the last time you saw a bad review in a car magazine?

Also, about FMUs and RR FRPs:

A true RR FPR will raise fuel pressure as a ratio to boost. Like 3psi for every 1psi of boost. And that ratio is sometimes adjustable. I've never looked into FMUs, but I'd imagine they work in a similar manner.

[This message has been edited by FieroJimmy (edited 02-19-2008).]

The rising rate boost referenced FPR's are adjustable with internal discs that give you anything from 1:1 to 12:1. Of course the discs are extra $$ if you want more than one. The supercharger guys like Paxton use them so the ECM does not have to be reprogrammed therefore making the car smog legal. Now I don't know anything myself, just reading the different websites.

The stock FPR is left untouched.

I know how the FPR works, and it makes sense that the boost pressure would assist it in raising the FP. Thats what I understood before I started searching the web. Some say that the OE FPR wont recognize boost, and this goes against what I originaly thought, as well as what you said earlier. Thats why Im getting confused, trying to figure out why it wouldnt see boost. So lets just ignore them, eh?

Now, the stock regulator doesn't really increase more fuel. It maintains base fuel pressures when fuel is spraying from the injector.

For example, 45 PSI base pressure at the fuel rail minus the 10 PSI positive pressure in the intake manifold = 35 psi of fuel from the injectors due to boost fighting against the injector itself.

The stock regulator, a 1:1 rising rate will maintain 45 psi firing out of the injector. 55 PSI rail pressure fighting against 10 PSI of manifold pressure will still result in only 45 psi exiting the injector.

So in order for me to see any gains, I would want an FMU / RR with a 6:1 ratio or higher, and the stock reg would still control FP under vacuum situations. Make sense?

[This message has been edited by AutoTech (edited 02-19-2008).]

what about blocking off the hole that the CS injector goes into and putting it somewhere else? like just before the throtle plate or something?
just an idea, i figure it could be re-routed easy, just some SS line and a compression fitting to splice into it it and you could move it almost anywhere.