Don Carter

So looking at the WSM diagrams, something I probably should have done yesterday, but who needs directions? .... basically what I did was install an 88 FPR in a way that fuel would flow opposite of how it's supposed to flow. The normal outlet that sends gas through the cooler and back to the tank, is now the inlet from the fuel pump. Now I understand why I'm getting no pressure.

Don Carter

Engine started with the orginal damper reinstalled at the front of the engine. It idles smoother, but stuttered when I tried to rev it slightly. I won't drive it with the stock FPR. Rail gauge is only showing 30psi.

PorKen

Rail pressure varies by vacuum and fuel temperature.

At idle, when manifold vacuum is high, the FPR reduces fuel pressure to keep the injected fuel volume constant.

Pressure also varies by fuel temperature. Cold +3 psi <-> nominal <-> hot -3 psi.



If you are using an Adjustable Fuel Pressure Regulator, I recommend setting the fuel pressure when the engine is cold, engine off, with the fuel pump relay jumpered, to 58 psi.

Don Carter

928Intl quickly shipped me the correct used 87 FPR, I installed it this evening, start her up, no leaks from the fuel line replacement, idling nice, rail gauge reading 60psi, so I take it for a spin. Within a couple of blocks from the house, it shifts with a nasty thud and immediately I realize I've knocked lose that freaking vacuum line to the tranny again...2nd time I've done that when working in that area. O well, should be an easy fix in the morning and I'm off all day to drive it :-)

Landseer

Nice, let us know how it delivers power.

velocipus

Holy Smokes Ken! I order the chips Wednesday night and found them in my mail today. I wish everyone offering parts for these cars were as on top of it as you!

Please make up some more PorKensioners so Roger can send it out to me and I can put my car back together (that is my parts ordered from another vendor ever show up Grrrrr!!! I'll be doing all my biz with you and 928s R US from now on.)

PorKen

Mind the gap!

I found that my old gapping pliers weren't very accurate. I've been running a 0.032" gap this whole time (WSM 0.027"/0.7mm-0.032"/0.8mm)! The bigger gap makes a noticeable difference in power. (Don't tell the other kids! )

The stock system with resistor plugs handles this just fine. Wearing to 0.35" should be OK.

Mike Frye

um. What?

Mako 928

I am going with spark plugs

svp928

Ken, which gap spec is better on these things? What brand plug are you applying it to?

PorKen

Steve - if you are using Bosch WR5DC, then gap them to 0.032"/0.8mm.

I'm using proper feeler gauges to verify the gap before I put them in, now.




Now, if you go to non-resistor plugs - say a NGK BP8ES gapped to much larger than stock 0.040" - and retune for the better spark...







(SAE)


Note that I've changed to a Y-pipe and a single pipe catback from an '84. This made it quieter, but in itself didn't make any more power than the X-pipe w/'85 catback.



(SAE)

Darklands

Ken ,
fantastic numbers ! :-)
My car runs way to rich ! I think the big TB makes the A/F ratio rich .
My exhaust tips are black inside and My favourite mechanic ask me how much gasoline the car consume after inspecting the pipes !

Oh,I forgot the highlight !One header has a crack and the car sounds like a Tiger tank .

PorKen

Karsten,

Have you checked the fuel pressure? I had a problem where the return hose from the FPR was too long so it kinked (squashed at the apex), and it ran rich.

How do the spark plugs look? They are a better indicator of the way it's running.

If the crack is large enough, the O2 sensor will keep adding fuel to go with the air entering the header?

svp928

Ken thats a great result for a mostly stock 85!
Well, I guess I'll get some Bp8's and try it out...

PorKen

The 'big' gap really changes the character of the engine. In order to run that big of a gap with the stock ignition system, you need to get more energy out of it, hence the non-resistor plugs. The non-resistors aren't a problem with the stock fuel and ignition brains/amps. (I did have a problem with aftermarket ignition amps that couldn't handle the RF, aluminum bases versus Bosch steel.) I don't have a radio, so I don't know if it makes static.

Part throttle performance is greatly improved. It revs way faster. It idles higher. WOT AFRs are leaned out. It can handle more advance in some places. I made new chips to go with the new plugs to get the most power out of it for the dyno result above.

I had to raise the programmed idle speed because if you adjust the idle down to 700 rpm, there isn't enough extra air for the idle recovery, and the rpms drop too low if you let off the throttle sometimes with the five speed.

It is more consistent on the dyno with the big gap. All three runs were within 1-2 hp and tq. (With the old plugs, the dyno runs would vary 5 or more.)

Bosch doesn't seem to make non-resistor anymore, so I switched to NGK. The NGKs are also nice because they go a lot colder in heat ranges.


My new mantra is: go with the coldest plug you can use, with the biggest gap that doesn't flake out at high rpm.