Real boost only above (exactly) 4000 rpm?

[Jonas_R]

Could you please list all mods that you have done and any info on chipset
I think that would help in solving the problem.

Do you have a boost gauge? What does it show?

[Jonas_R]

Could you please list all mods that you have done and any info on chipset what boost levels and at what rpm
I think that would help in solving the problem.

Do you have a boost gauge? What does it show?

[OrMar]

faulty knock sensors on the 7A make it feel flat until you hit EXACTLY 5000rpm then it goes like a scalded cat. So in that respect yes it could be knock sensors. You can run them disconnected but i would only do it to test for a short period to see. Assume you have vagcom'ed the car?

Replaced both knock sensors with other items, but no luck. Will try to disconnect them and try then. VAGCOM shows nothing.

[OrMar]

Could you please list all mods that you have done and any info on chipset what boost levels and at what rpm
I think that would help in solving the problem.
Do you have a boost gauge? What does it show?

Well, I don't think it's in direct relation to my RS2 modification because:
- car was going like it should with standard components and ULTIMOT software
- then I had engine rebuilt (mechanicaly), and immediately afterwards lost boost under 4000 rpm, still with standard components
So, my guess is my mechanic (who isn't an Audi expert but I trusted him because he was doing my Alfa's for me and he said he can do it) did something wrong while rebuilding.
Rebuilding was more or less standard: new H-rods, RS2 bearings, new piston rings, new cams chain, ..)

Later I upgraded to:
- RS2 turbo
- RS2 exhaust manifold
- 034 RS2 replica injectors
- 4bar fuel pressure regulator
- 3 bar motorola MAP
- big FMIC
- 044 fuel pump
- software which is said to be compatible with this configuration, bought from a guy on german meckis forum

I have boost gauge, car starts and drive OK, expect there is no more than 0,4 bar of boost under 4000 rpm. Immediately as I pass 4000, it raises to 1.7 and more, but there are some hesitations once above 1.5 bar (will resolve that, my guess is my piping just isnt 1.5+bar-proof).

Mario

[Jamo]

Disconnect the N75 valve and get a manual boost controller or borrow an electronic one

See what the boost profile is like, could be the chipset has no duty on the N75 untill late rpms

[Billman]

Check the MAF sensor! Motronic uses it on part throttle and low rpm. After that it runs on standard map without MAF input.

[OrMar]

Disconnect the N75 valve and get a manual boost controller or borrow an electronic one

I tried to simulate manual boost controller with 1.9 bar wg spring. Nothing changed under 4000 rpm.

See what the boost profile is like, could be the chipset has no duty on the N75 untill late rpms

Iz was the same with other chipset which was working OK before engine rebuild.

[OrMar]

Check the MAF sensor! Motronic uses it on part throttle and low rpm. After that it runs on standard map without MAF input.

This could lead somewhere - do you maybe know at what rpm is "separating point" for that functionality ?

I have tried few different MAF-s and car did change it's behaviour (had some lean mixture problem at high rpm also), but not under 4000 rpm. Maybe I have bad MAF connection to ECU or something, will check.

[Jamo]

I stand by my original thinking then, the cam timing is wrong.

MAF wont do anything to turbo boosting characteristics.

[OrMar]

Could you, please, explain in detail your cam timing check procedure; maybe we are doing something wrong ?
MAF won't directly impact boost, but what if it send wrong air information to ECU, ECU don't deliver enough fuel and there are simply not enough exhaust gasses as a result to produce boost ?

[prj]

Check the MAF sensor! Motronic uses it on part throttle and low rpm. After that it runs on standard map without MAF input.

Sorry, but that's completely wrong. The MAF is used at all times. Please don't make such statements when you have not looked at assembly code of LOAD calculation in Motronic.

I have tried few different MAF-s and car did change it's behaviour (had some lean mixture problem at high rpm also)

That could mean wrong mapping or MAF maxing out.
A 3B I was mapping recently with 3076 Turbo had the MAF max out already at 4500 RPM, and after 6000 RPM went really lean, because ECU thought that load decreased, since the MAF value remained the same at 5.56V.

No power on low RPM's can be due to too rich mixture, perhaps you have bigger injectors or bigger fuel pressure than specified in the chip. The guy with the 3B, that came to me, had exactly the same problem. 10-11 AFR at idle (with lambda turned off) and 15 AFR under boost. No power below 4000 RPM... it drives much better after mapping it.

[Billman]

Sorry, but that's completely wrong. The MAF is used at all times. Please don't make such statements when you have not looked at assembly code of LOAD calculation in Motronic.


That could mean wrong mapping or MAF maxing out.
A 3B I was mapping recently with 3076 Turbo had the MAF max out already at 4500 RPM, and after 6000 RPM went really lean, because ECU thought that load decreased, since the MAF value remained the same at 5.56V.

No power on low RPM's can be due to too rich mixture, perhaps you have bigger injectors or bigger fuel pressure than specified in the chip. The guy with the 3B, that came to me, had exactly the same problem. 10-11 AFR at idle (with lambda turned off) and 15 AFR under boost. No power below 4000 RPM... it drives much better after mapping it.

Sorry dude! That's what a tuner told me... And yes I didn't read the motronic load calculation maps! Don't have to!

[prj]

Then your tuner was wrong, at least for the Motronic used in our cars.
And I am not talking about maps, I am talking about how the initial LOAD value is calculated from the MAF signal. That is also one part of why there exists the limit of ~400hp on Motronic without replacing or messing with the MAF.