Losing boost at 6400rpm. Help!

[tissimo]

He's now runniong a 2J MAP sensor instead of a 1J. I think that there is a scaled difference between the two.....

That wouldn't effect anything. Unless he has the ecu setup for one and the other is actually scaled wrong (but that wouldn't be the boost fall off problem). The JZ sensors are pretty weak though (only like 2.3 bar) and should swap out for a 3 bar or the like.

 

[rakkasan]

That wouldn't effect anything. Unless he has the ecu setup for one and the other is actually scaled wrong (but that wouldn't be the boost fall off problem). The JZ sensors are pretty weak though (only like 2.3 bar) and should swap out for a 3 bar or the like.

Actually, I think it is set up that way and now he's seeing boost cut because of it (?). I suspect that his problem is sensor related even if I am wrong....

 

[IJ.]

I've given J instructions on how to test the Map sensors using a compressor so once he's tested both we'll have a better idea if it's the fault.

 

[tissimo]

I've given J instructions on how to test the Map sensors using a compressor so once he's tested both we'll have a better idea if it's the fault.

Do you mean the boost fall off on 'it's the fault'.

I would assume he verified his Datalogs with his avc-r boost readings as well.

 

[IJ.]

It's J who knows

 

[suprahero]

Do you mean the boost fall off on 'it's the fault'.

I would assume he verified his Datalogs with his avc-r boost readings as well.

The only thing that I can verify at the moment is that while dynoing my car, the AVC-R never fluxuates. It never shows a loss in boost pressure, but the datalogs do.

 

[tissimo]

The only thing that I can verify at the moment is that while dynoing my car, the AVC-R never fluxuates. It never shows a loss in boost pressure, but the datalogs do.

Well, thats the problem then. Check the vacuum lines to the stock map sensor then. Put zip ties on all the connections to make sure they dont balloon and blow pressure out.

Where is your AVC-R plumbed in compairison to your map sensor?

You technically aren't losing boost, you're sensor is giving a miss reading.

 

[suprahero]

I'll have to go check Justin, but I think they're both plumbed into the back of the manifold. I know the map sensor is, and I think the avcr boost sensor is also. I can go check right now though.

The map sensor does have a zip tie on it, but it's never felt super tight to me.

 

[IJ.]

If the scaling is different between the 1 and 2J map sensors it's possible that it's showing a drop off in boost or going into cut, this is why I asked J to test both with compressed air so we'll KNOW what's going on instead of guessing.

 

[suprahero]

It hasn't quit raining Ian or I would have tested them this evening. I haven't left the house to get a regulator either. I will try and get one tomorrow though.

 

[tissimo]

If the scaling is different between the 1 and 2J map sensors it's possible that it's showing a drop off in boost or going into cut, this is why I asked J to test both with compressed air so we'll KNOW what's going on instead of guessing.

IMO just stop messing with the stock map sensors and get a real one. He has a standalone.

 

[suprahero]

What would you suggest Justin? I've read people getting a GM 3bar map sensor. Is that what you'd get?

 

[IJ.]

IMO just stop messing with the stock map sensors and get a real one. He has a standalone.

Ditto been using Delco 3 bar sensors for years now.

 

[suprahero]

Can I buy one at an auto parts store, or will I have to order it online?

 

[Turbo Drifter]

GM 3 bar map sensor is a common sensor to use on Standalones. I was under the impression you were useing one already. This is starting to make great sence now LOL!!. All this for nothing really you are just hitting the 5V max on that sensor and its not reading any more than that.

If you install the 3 bar GM map you will need to retune your car to it. Do not boost with out tuning first!!!

Jeremy

 

[suprahero]

I'm not getting my hopes up yet. You don't know what I've been through.

New wastegate, YEAH!!! I got it fixed.............not
New intercooler pipes.YEAH!!! I got it fixed.............not
New turbo..........YEAH!!! I got it fixed.............not
New vacuum lines...YEAH!!! I got it fixed.............not
New blow off valve..YEAH!!! I got it fixed.............not

I'll fix this tomorrow and see if it helps any. I don't know how a map sensor would just go bad, but maybe it did.

 

[tissimo]

As I said in the PM yes, you can get a GM 3 bar map sensor at the parts store. IIRC Its a 89 Turbo Trans am/Firebird map sensor.

If you install the 3 bar GM map you will need to retune your car to it. Do not boost with out tuning first!!!

Jeremy

You can rescale your current map to give you nearly what your tune was before, but yea a retune to make sure everything is good wouldn't be a bad idea.

I'll fix this tomorrow and see if it helps any. I don't know how a map sensor would just go bad, but maybe it did.

I dont think it went bad, it just has a bad vacuum source I think. You can probably Redo the vacuum line to the map sensor and get rid of your problem. Use a dedicated line with no Ts off of it for the map sensor.

 

[IJ.]

J: Please do the tests I PM'd for my own peace of mind.

 

[suprahero]

Thanks guys. I'll do the tests Ian. I'll see if I can find a regulator at WalMart and test them each.

 

[Turbo Drifter]

I'm not getting my hopes up yet. You don't know what I've been through.

New wastegate, YEAH!!! I got it fixed.............not
New intercooler pipes.YEAH!!! I got it fixed.............not
New turbo..........YEAH!!! I got it fixed.............not
New vacuum lines...YEAH!!! I got it fixed.............not
New blow off valve..YEAH!!! I got it fixed.............not

I'll fix this tomorrow and see if it helps any. I don't know how a map sensor would just go bad, but maybe it did.

I belive I have been trying to help you with this since the first page....I know lol.

You're MAP sensors are not bad there just 2 BAR Absolute MAP sensors. Once you hit 1bar guage they are at 5V and will not read any higher. This is why you do not see the drop on the AVCR.

Jeremy