i really don't think that it has to do with boost spike and fuel, mainly because ive seen the kit put to use in high boost like 9 psi and have no probles, HAVE to be abuse beyond what it can handle and installs

 

If it runs 80% IDC at 6psi, I have little faith above that. Yes, I know...fuel pressure, but 80% IDC is on the cusp of being dangerously high. And considering the overall lack of precision in the fuel delivery system...well...I have my doubts.

 

Not spikes but creep. A MBC or EBC can correct that issue.

 

As stated in an earlier post (just started reading thru this thread) Larger exhaust piping can cause boost creep, different than spiking. I see that you have a turbo back. This is a common thing that happens when you start upping the diameter. Most commonly, At least for DSM's is when you replace the down pipe. No boost controller is gonna combat that problem. What you need to do port out the O2 housing or go with an elimantor pipe that replaces the entire O2 housing and down pipe as one piece. Looks like you are just out flowing things. You know that you have creep when you have the boost level predetermined by one means or another and it steadily rises past that point. You just cant get rid of the excess pressure. You are increasing your exhaust flow when upping the exhuast piping and the gate just cant keep up.

 

That doesnt sound right. I thought all it shared was the housing, different wheels.

 

That was just what I found when I did some searching on the net. I've heard some feedback to the same from people as well... but at the least we know that the T28 is somewhat in between the T25 and the T3 (DUH!). I think the big question that it would be good to know the exact answer to is what compressor is in a T28 so that we could get maps for it.

 

Isnt a t25 just that a t25? And the t28 too, big or small? At times could either be just another Super 60, in some cases, smaller t3 wheels can fit or could some build them as a t25/28? There could be many combinations I dont think you are really gonna get an exact answer but most likely only a hand full of good combos. The big t28 uses the largest t28 wheels available on each side. So basically, not talking super 60's, a t28 just uses a t25 housing (hogged out) and shaft with t28 wheels...and the Big T28 uses the largest t28 wheels.

 

I have a question regarding ignition timing and boost. Since you're here Mobius maybe you'd know. If not, maybe someone will pick it up later. Is there a mathematical formula for it or is it more or less trial and error to prevent knock a little and still accelerate/drive smoovely. (not to be confused with smoothly )

Man, I've gotta stop posting before I'm done with a thought.

Anyway, I'm kinda assuming it's trial and error, but doesn't that mean it'll be very difficult to advance/retard in areas of the ignition map you don't normally drive in? (like let's say -0.5bar and 6000rpms) But if you were to hit the point later in driving (granted this one is a bit extreme) couldn't it cause a bit of a suprise?

 

I think that you are going to be stuck with trial and error, seeing every car is different. I myself am not too versed in this area but from what I know this is most likely the case.....perhaps try one of these methods: using higher octane gas, better cooling or lowering your boost. I guess is it just finding a balance that works for your car. Maybe there is some formula but I doubt it. Here is some info that might help written by someone else:
OK, if I can easily adjust boost, spark advance, and mixture ratios, (and to a certain extent
inlet air temp) what should I have more of to make the best power?

Excellent question. I don't know. I suspect that boost is worth more than spark advance, with
mixture ratio somewhere in the middle. If I had a PMS, a datalogger, and a dyno, I think I'd
set spark advance to about 2/3 of the possible range the computer provides, set the mixture a
little on the lean side, and then run the boost up to the detonation point, and back off a
little. Then I'd play with the mixture to see if I can get more power, or get the motor to
stand more boost. Once I've got a good WOT boost level and mixture ratio, then we see how much
more advance it can take. Maybe.

Note that we haven't taken inlet air temp or density into account here, nor have we allowed for
real-world factors like: how fast can the wastegate react to boost spikes? This is just an
educated guess. Bottom line? Lots of testing. Lots. And you can't get the inlet air temp too
cold.

 

I don't have a knock problem. I'm just learning before it becomes an issue. Air temp and density aren't really serious factors for me at present because I'm using a MAP sensor and I'm not knocking, but I figure it's best to ask before I need to ask. Still struggling to find the time to revise my maps and iron out some minor inconveniences like engine startup, some idle fluxuation and fuel when approaching positive pressure. At the same time I'm going to be redoing all my vac/coolant lines in the near future to eliminate the possibility of them leaking, and I'm awaiting my Defi Link system from Gruppe-S (apparently white faced 52mm gauges aren't usually in stock so they had to special order them for me) so that I can monitor fuel pressure and get more precise EGT and boost/vac readings. I think my boost gauge is reading slightly low and my EGT probe placement makes it useful only as a reference point for change.

I have a GReddy Profec B Spec II installed but not operational at the moment (I lost my booklet), but the Turbonetics wastegate I have is known to be problematic, so how it's behaving is a variable that I can't presently account for.

I keep feeling like I'm hogging this thread with my own questions, but hopefully other people will learn and benefit from them as well. I've been a gineau pig thus far, why stop now? Anyway, I appreciate the help as always, Mobius. Thanks.

 

Antyime!! Sorry I couldnt be of more help to you.

 

Ah, resurrection.

So an update on my fuel situation. I had serious stutter at around 0psi when my FMU was kicking in. I should say "have" because it's happening presently as well.

So here's the scoop after a little data logging. My AFR was crazy lean (16.8:1) at certain points (low RPM's, in vac. not under boost)so I'm going to fix that as soon as I can.

The problem around 0psi seems to be quite the opposite of what I thought. I was thinking I wasn't getting enough fuel and I was running lean. Turns out I'm running 8.2:1 AFR as the FMU kicks in. Under boost my AFR varies from around 11.2:1-12.9:1 (where it should be according to my map). When I get my new injectors and my defi-link gauges I'm going to test out my fuel pressure and whatnot, see how high it's getting, and then lean out my fuel map in that area. Still hitting 17.6:1 AFR at 5+psi and max bits on the fuel map with 650% boost correction...still gotta figure that one out. Just thought I'd give an update since pretty much everything I've posted here has been regarding my gineau pig...I mean car.

 

what size are your injectors now?

 

Still 440cc.

 

so you've maxed out the fuel map for 5 psi and above yet you are still running a 17:1 ish fuel mix? damn.. that's flippin lean for that much boost. Definitely will be curious to see what your fuel pressure come out at once you get those logged. the injectors are plenty plenty big for what you have...

I hate to suggest this... but it is one way around the problem... and I've seen it done. Get a new manifold with a second fuel rail. Then you can set up programming to only engage that second fuel rail when things go lean. That way you can overcompnesate while keeping fuel pressures low and make life a little bit easier. It's a bit of a costly add though, and I don't know the programming necessities off hand... but just a suggestion of course

Later.

Steve