So I just broke 1000 miles on my rebuilt 89 T2 on the way home today and decided to start giving it a little boost. The AFR's have been showing nasty rich conditions the entire time and I figured that they may go away as the engine breaks in more, but no, obviously they didn't. So here's the skinny:

Cruising at 20-25% throttle the AFR dips from mid 12's to low 11's / high 10's then climbs and rests in the 13's until I switch gears and the pattern happens all over again. I have lately started seeing some 14's on the board... occasionaly.

When I started boosting, it took a while for the guage to even get past zero, like up to 35% throttle, then it took forever to build up even 5lbs of boost. I didn't want to take it any higher than that, same with the rpms... I switched gears around 5000. It doesn't feel like I'm getting much power either, like almost nothing. The AFR's got down to low 10's when I boosted at 5psi..... a liiiiiiittle too rich.

Before I popped the motor, the car was tuned pretty well using a S-AFC, AFR's were great, boosted easily and acceleration was great. My first thought is that I need to re-tune it, but no alterations were made to the way the S-AFC handled the fuel when it was rebuilt.

Mods:

PYX Wideband
S-AFC
FMIC
720cc secondaries
Walbro 255
Profec B
RB downpipe
Rat's nest removed

Sparkplugs are new, wires are in great condition.

Thanks in advance guys,

Al

 

Oh yea, turbo is stock and in good condition.

 

boost leak?

 

Timing?
I echo the boost leak question.
And, are you using your previously tuned map on the SAFC or is it blank (let's the stock ECU do all the work)? If that SAFC was the only thing cutting out fuel (because you would cut fuel while using larger injectors to get the right amount under boost levels that the ECU is prepared for (vacuum to ~8psi boost)) then you would run crazy rich if the SAFC were no longer changing the AFM reading.

 

clean or replace your air filter. Do a test, remove the air filter and run the car, if the problems goes away, the problem was the filter.

 

Just don't drive through puddles, dust, on gravel, et cetera...

 

How long did the car sit during the rebuild? Your injectors may be gummed up.

Also if you drove the engine very easily for that 1000 miles, it will still be breaking in and compression will still come up.

 

I vote boost leak as well

 

The timing is on, air filter is clean, and it's still using the same map from the S-AFC before the rebuild; nothing was touched there.

The car sat for about two and a half months, and the primaries are still the stock 550's, so it's a distinct possibility that those guys are dirty, I'll look into that. I've been babying this motor for the last 1k, and intend to slowly work it up to redline / full boost for the next 1k. How long do you think until compression reaches it's peak?

If it were due to a boost leak I'd be suprised seeing as there are brand new gaskets, everything tightened down real nice. Wastegate stuck? It wasn't intentionally held open, but maybe it's stuck after sitting there for a while. I'll go grease it up tomorrow and see.

Thanks for the replies!

 

If the wastegate were stuck open it wouldn't run rich though, you'd just lose power.

 

^^True. Before the build I had suspected that my ECU had blown from the OMP; I just pulled back the carpet to take it out to check and see for sure and I could see the computer fried up. Megasquirt is about to go in anyways. OMP is currently blocked off and just hanging.

Could that be the reason for the richness? But the S-AFC is controlling the fuel, and the Profec is controlling the boost. So I'm thinking injectors more now, and since it's gummed up so rich it's not building boost as fast cuz it's not making as much power initially. That's just jumping to conclusions, I'm thinking as I type. Where else would a possible boost leak come from?

 

!!!!! I thought you would have known this. From what I've read, the S5 OMP HATES being disconnected, apparently your ECU will freak. Search 'limp mode OMP', that might find you some info.

 

i assume he has it connected.
http://www.boostpro.net/prodtester.html
i bought this last week, VERY nice leak tester!!

 

Yes, of course the OMP is still connected; it's just not attached to it's spot...

So I tried removing some fuel with the S-AFC last night when I was driving and it helped, brought it up into the 14's nicely. However this afternoon I was driving and it wasn't in the 14's anymore, it was back to the same old ****.... I'm stumped.

Now, I forgot to mention that after boosting the AFR's will be normal for about thirty seconds, then go to crap again.

Oh well, megasquirt will be going in a week from now. OMP will finally be COMPLETELY removed, and hopefully it will get rid of anymore ghosts in the system. Then it's on to constructing a new wiring harness. Get that 20 year old stock-corroded-piggybacked **** outta there!!!