Map Tracer Query

[benl1981]

I've asked this in other threads but haven't had any luck as yet.

I have a bit of reversion from a high flow turbo.

One of the things I notice on the map trace if you hit it in 2nd (or any gear >1st) and then back off - i.e. rev to about 4 or 5k and then back off the fot doesn't go straight back to the top - there is a slight delay. THen when it hits the top It shoots back down the vertical axis for a second or so even with the throttle closed.

Anybody with stock or other turbo - have you noticed this?

Also going up a hill in 4th gear hovering around 0-3psi you can see the dot flutcuating between about 3 or 4 load points in the vertical axis with a steady throttle opening.

Thanks

[paulr33]

covered in the PFC FAQ in my signature, have a read of it, tells u how to use map tracer and explains what it tells you

[benl1981]

I know exactly what it does and how to use it. My problem is more specific than what is in your sheet.

[paulr33]

the map tracer movement is based on LOAD

which is derived from AIRFLOW and using load correction calculations. TPS doesnt control the laod axis, so its purely the AFM doing that

[benl1981]

I know that!! I am trying to troubleshoot a particular problem

What I suspect is happening is the turbo is delivering too much air and flow reversion is occurring where the engine can't consume all the air.

Most of the time at lower loads (in load points 2-6 I can hold the dot in the same box going up a hill - i.e. hold the same load). As the load increases I feel the turbo may be spooling too - as you go up to load point 9 etc in4th gear the AFM voltage is fluctuating a lot!

Can anyone answer the questions I posted and check their map trace.

I don't think what I described is normal but I never checked it that closely with the stock turbo.

Edited June 18, 2007 by benl1981

[benl1981]

bump

[benl1981]

anyone..sk?

[benl1981]

Come on. Somebody must be able to check their map tracer?

Thanks

[benl1981]

pretty please

[BHDave]

Yes, It sounds like you are experiencing fairly mild compressor surge (it must be mild if you can't feel it, only see it on the map trace).

I haven't watched it in that situation, but i have logged my afm voltage before (when i had no bov) and watched the numbers bounce around all over the place when i lifted the throttle. In my case, basically, big spike, down to nothing, not so big spike, down to nothing.....you get the idea.

I can get mine to chuff away quite happily in similar situations (partial throttle, up hill), though generally 3rd gear, 5000rpm or so.

[benl1981]

Sometimes I can definately feel it - but that's when it jumps about 5 or more cells in one hit straight down the vertical axis.. So with the BOV attached did you still get a similar effect.

What spec turbo do you have and on what engine?

Cheers

Edited June 27, 2007 by benl1981

[MANWHORE]

Ben, I'm not sure of the specs on your particular highflow, whether it's the same as the current gcg. Nor do I have a powerfc, so I can't comment on the map tracer.

If you fit a pod filter on and when you're flooring it, do you hear flutter as the revs are rising? not when you take your foot off. How bad is the compressor surge?

[Cubes]

As I mentioned in your previous thread I've seen and experienced it on stock turbo'd cars, highflows and GT35r's with and without a bov.

Without a bov it is much more severe; with the factory recirc it only occurs under specific circumstances; you can drive around it easily.

From my understanding of your problem it isn't so much compressor surge but rather the air travelling backwards through the afm, so reversion as you say. But yes.. There is compressor surge in there but its not the compressor surge causing the drivability problems but rather the air hitting the afm be it via the dump of the recirc bov or the air travelling backwards through the turbo and out past the afm.

I've found running no mesh on the turbo's side of the afm does slightly increase this reversion so to speak.

The fix from what I've found.....

1. Drive around it/change your driving style - This is the big one.

2. Atmo Bov (but you then have overfueling stalling as a result)

3. If your running no bov reconnect the stock bov to reduce the intensity and frequency of the afm reversion.

4. Larger dia. afm to turbo pipe or if possible longer.

A 4" afm to turbo pipe appears to work well in reducing this afm reversion.

[Adriano]

To try and reduce the reversion in the AFM, you could build an anti reversion cone into the intake pipe. Im going to do this on my gtr with these pipe sizes

____________

____________ / : : \_______

____/ : :

: :

Turbo 4inch 3.25in : 5inch : 4inch Air filter

: :

____ : :

____________\ : : _______

\__:________:_/ The AFM is in the 5 inch bit, so i helps that im running a 5in AFM

The : is mesh(like the standard stuff except thicker)

[Adriano]

Gee that didnt work, if you want to see what i mean, just click on reply to the post, and itll make sense

[Cubes]

A little pic of the above..

[rob82]

To try and reduce the reversion in the AFM, you could build an anti reversion cone into the intake pipe. Im going to do this on my gtr with these pipe sizes

____________

____________ / : : \_______

____/ : :

: :

Turbo 4inch 3.25in : 5inch : 4inch Air filter

: :

____ : :

____________\ : : _______

\__:________:_/ The AFM is in the 5 inch bit, so i helps that im running a 5in AFM

The : is mesh(like the standard stuff except thicker)

It may work - could also compound the problem via increasing the air speed as it necks down to the AFM. Whats to say it wont cause reversion as you back off ie in stead of the turbo and engine inducing the air in it reverts off the 3.25in section. You could do what the EF falcons do via introducing a helmholtz resonance pipe on a particular bend. different theory but it should work.

[benl1981]

Gee - I find it odd to think I have to modify the intake so much. I guess it may beat taking the turbo off and having it reworked.

Cubes..Can you still have the stock air intake - i.e airbox and still do that you think?

Bit of farting around.

[Adriano]

That setup is what im going to run on my 450RWKW gtr, so the sizes could be turned down for an rb25

[Cubes]

Ben,

Its possible. All though I run a stock airbox with a 100mm cai I don't see why you couldn't run a larger afm->turbo pipe on the rb25.

With the larger afm->turbo pipe + retaining the mesh on your afm + retaining the stock bov + ensuring you haven't blocked up the bov's bleed hole the reversion is basically non existant apart from a few select driving conditions. That was a mouth full.

Yours may be a little more touchy I'm not sure but...... (<<< Lots of dots for those who care lol)

You obviously know how to get it to do it... Have you tried to adjust your driving style to prevent it and just accept the fact that its part of owning a modified car?