Load Very Jumpy at WOT, need MAP Filtering?
 

I'm working on a Haltech E8 and under boost the load is really jumpy. I'm wondering if this is the kinda thing where MAP filtering would help. I haven't tried it yet since I don't want to mask a problem if there is one. Any ideas? I have included an image to better show what I mean. Thanks.

https://www.rx7club.com/attachment.p...1&d=1248368126

thewird

What kinda MAP sensor and where's it hooked into on which car?

That looks like an issue with something other than the ECU.

Its a GM 3 bar map sensor. It is hooked where the stock MAP sensor would normally go.

So I ended up testing the Haltech MAP sensor filtering. I set it to the setting that would have the least affect on idle which is the max 50 setting. As I reduced the number the reading would become less and less accurate and idle would go to shit because of it. So the max setting of 50 was used.

Anyway, I did a pull and it did help smooth out the boost as shown below. However, it added a tad of MAP sensor lag. That is when quick changes in load would occur, the car would hesitate like idle --> WOT, cruise --> WOT etc. So obviously this is unacceptable.

https://www.rx7club.com/attachment.p...1&d=1248391675

So then I considered the signal wire was getting some noise and changing the signal. The whole wiring was wrapped around with tin foil and a wire wrapped around that and grounded to the chassis. Also pulled the wiring through the firewall as there was a lot of excess wire in the engine bay that didn't need to be there. I then went out for another pull and this did indeed help. However, the problem still remains, just not as drastic changes in load. The pull is shown below...

https://www.rx7club.com/attachment.p...1&d=1248391888

So now I think it still might be noise. There is an excess of 5 feet of cable of the wiring for the map sensor. Tomorrow we're gonna try to shorten it to the proper length and see if it helps. If the problem persists, I will try my map sensor which is the same. I'll update on whatever I find.

thewird

Forgot to mention something. A filter was also added in the line and the map sensor was turned down since it was pointing sideways trying to fix the issue as well.

thewird

Couple things I would try:

Tee into the MAP sensor line with something like a mechanical boost gauge. Watch it and see what it does, does it jump in the same manor etc?

Tap the map sensor into another vac line (this is an FD I'm presuming?) and see what happens.



Is there any AI on this car? Sometimes water can cause funny issues in the sensor, but if you've turned it downward chances are its fine moisture wise......but wouldn't hurt to blow out the line a bit an reattach it.

I have to say I have never seen this and am very curious what your solution will be. I agree with the above but I always use the stock nipple on the FD and have never had this kind of result. Good advice above. I have actually seen boost control issues give a similar MAP response but with the amount of swing you're seeing in what the MAP sensor is telling you the pressure actually is you should be able to hear/feel the power surge if the pressure is actually changing that much.

It's actually a FC. I don't think the boost surges are actually happening. The reason I say this is because when I enabled MAP filtering, the car pulled very smoothly through the RPM range. When I do pull without filtering, I can feel the car power changing slightly but that is due to timing and fuel going up and down. Also if you notice the surges are instant drops or instant climbs.

I didn't think about testing it with an actual pressure thing. I'll try that today too.

thewird

Marco, if this is an FC:

Make sure the MAP sensor is connected to the front of the UIM, on the TOP nipple it provides the cleanest signal.

Ok, so after shortening the wire and shielding it again, there was no difference. I then set the nipple to where Joe suggested for a boost source and here was the result...

https://www.rx7club.com/attachment.p...1&d=1248478854

So its noticeably much better, however it is still pulsating. Is this how a Haltech boost log should look like or should it be smoother? It is affecting the timing by 1-2 degrees and the fuel too but not really noticeable. Any other ideas :dunno:

I'm tempted to finish tuning it like this but I don't really want to...

BTW, thanks Joe for the suggestion.

thewird

Is it possible the actual wastegate may be pulsating as its still the stock turbo internal wastegate and control mechanisms?

thewird

Hmm very possible.

I would try the cheap boost gauge method (IIRC, I've got a cheap autometer mechanical around here if you need to borrow it....) now that the nipple situation has been looked after. Watch the gague and see if the manifold pressure is indeed pulsing, or whether the MAP sensor's output is still just hovering on its own.

Also, just as an aside, the wire length in this case shouldn't matter. The elcetricity is travelling at the speed of light down the wire, so length shouldn't matter too much when we're not talking about miles of cable :)

I'll test more on Monday since I didn't bring the car home. The car does have a boost gauge inside and it vibrates like mine does at full boost so I thought it was ok.

As for the wiring, that makes sense but I really didn't like 5 feet of unneeded wiring just hanging there lol.

thewird

glad to see my car is in the hands of a perfectionist...
and once its done being tuned its headed to classic auto :)

LOL, are you ever going to drive your own car :P

thewird

not funny you big jerk

I hide

http://www.coolfunnyanimals.com/thum...mal-cat-21.jpg

thewird