engine hesitation problems..

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JayRome

JayRome

Blurring the line between 1st to 3rd Gen engines..
Joined
Jun 14, 2006
Messages
4,958
Location
Melbourne
my car seems to flat line with power at some rpm levels and random hesitation.. and its now getting annoying..

i did some data logging tonight, and came up with some results....

its N/A + T and the ECU is having trouble controlling it, i have even retarded the timing to compinsate and still no go..

looking at the saved log, i have noticed that the stock VR4 Maf seems to max out . also no knock thats retarding timing..

short lits of mods go..
11:1 comp
EVO8 16g with short manifold
VR4 ECU
VR4 MAF
the shortest IC pipes possible
3" intake pipe from turbo to maf...
6psi
over sized pistons
1mm over sized valves int/exh

now the stats...
i cannot pass 65% throttle as the power will flat line but boost will continue to hold
so testing at 65% throttle
in between 5100rpm to red line
injectors at 87.5%
the MAF flat lines at 1603.9Hz and will not go any higher..
power also flat lines at the same time the MAF hits a max point..


so i'm thinking that all the power curve problems could be caused by the MAF and possibly the
stock ecu programing being maxed in some areas...

does anyone have a chart/graph of the stock afm with CFM vs Hz or the max and min paramaters of the stock MAF?

or would anyone know what would be the max HP/Kw a stock MAF would top out at?


cheers
Jay..
 
hi jay!

M0st of the data you posted here is just greek to me.
But i had s0me engine hesitati0n in my sohc 4g63 at around 1800 -2000rpm, when it passed 2000rpm the power came back.
Did a diagn0stic trouble c0des test with a test light and turned out that my TPS was faulty. Replaced it and the hesitation was gone

Maybe thats ur problem.
Wouldnt hurt to do trouble codes check


Cheerz
Dasith
 
What MAF is it Jay?
What ECU / CHIP / Tuning method Jay??

You'll obviously need larger injectors if they are already at 87%..
What are you af/rs?
 
Dasithkg said:
hi jay!

M0st of the data you posted here is just greek to me.
But i had s0me engine hesitati0n in my sohc 4g63 at around 1800 -2000rpm, when it passed 2000rpm the power came back.
Did a diagn0stic trouble c0des test with a test light and turned out that my TPS was faulty. Replaced it and the hesitation was gone

Maybe thats ur problem.
Wouldnt hurt to do trouble codes check


Cheerz
Dasith
Click to expand...

that is the one thing left on the car that is still stock from 1989... but i have reco'd it... although its not surprising if it is a lil faulty...


bazeng said:
What MAF is it Jay?
What ECU / CHIP / Tuning method Jay??

You'll obviously need larger injectors if they are already at 87%..
What are you af/rs?
Click to expand...


Stock VR4 Aspec Maf
and stock single board VR4 ECU, no chip, and no tune just bog stock, running highly modded engine :blink:

afr's would probably be shit house.. but havent checked, havent bought a wide band yet....

so it probably needs bigger injectors? but i wouldnt think the the ecu/maf would top out at 6psi? even on an N/A...
 
I'd get some method of tuning the car.
What about that microtech you have?

If you stick with the stock ecu, just ecm link + magna / evo afm.
What sized injectors exactly??

So you got the driveshaft / lsd working??
 
bazeng said:
I'd get some method of tuning the car.
What about that microtech you have?

If you stick with the stock ecu, just ecm link + magna / evo afm.
What sized injectors exactly??

So you got the driveshaft / lsd working??
Click to expand...


yer bro installed on wednesday, FWD LSD is mad fun to drive! really
sticks to the road, but i installed into a box that i dont remember the
history of. now i remember cause it crunches 2nd and 3rd.... so time
to rebuild one of my other spare box and transfer the LSD again....

i'm trying to stay away from the Microtech for drive ablility and fuel
cause i do alot of free way driving...

oh and i'm running stock VR4 injectors um... 450's?

i'm thinking of going EVO6 ECU but having a hard time finding just
the engine loom or ecu side plugs to rewire to my loom...
 
BMGTZ said:
Yep just whack an ecm in......they give you so much tune ability.

the dollars is good right now too............i just ordered three
Click to expand...

i'm thinking about it...... although i wonder if they will handle quad throttles well.......
 
Hey Jay, my cousin with the RS gets around 420k's a tank with a Microtech, and what he does is far from freeway driving :).
 
JayRome said:
my car seems to flat line with power at some rpm levels and random hesitation.. and its now getting annoying..

i did some data logging tonight, and came up with some results....

its N/A + T and the ECU is having trouble controlling it, i have even retarded the timing to compinsate and still no go..

looking at the saved log, i have noticed that the stock VR4 Maf seems to max out . also no knock thats retarding timing..

short lits of mods go..
11:1 comp
EVO8 16g with short manifold
VR4 ECU
VR4 MAF
the shortest IC pipes possible
3" intake pipe from turbo to maf...
6psi
over sized pistons
1mm over sized valves int/exh

now the stats...
i cannot pass 65% throttle as the power will flat line but boost will continue to hold
so testing at 65% throttle
in between 5100rpm to red line
injectors at 87.5%
the MAF flat lines at 1603.9Hz and will not go any higher..
power also flat lines at the same time the MAF hits a max point..


so i'm thinking that all the power curve problems could be caused by the MAF and possibly the
stock ecu programing being maxed in some areas...

does anyone have a chart/graph of the stock afm with CFM vs Hz or the max and min paramaters of the stock MAF?

or would anyone know what would be the max HP/Kw a stock MAF would top out at?


cheers
Jay..
Click to expand...

What VR4 ECU are you using? Are the pins correct? (there's some pin swapping business that usually goes on between the AU and JAP models, may apply to you ?)
Do you have any datalogs that you can send/convert etc? Doing a log at WOT would be helpful at indicating what could be causing the lack of power.
Unless you have a modified chip in the ECU, 1600Hz will come up pretty quick. Most chips have the MAF Hz shown on the logger halved so it will display >1600hz (just double whatever is shown).
Are you using stock VR4 or GSR FPR? (is there a difference?)
There is a possibility you could be overruning the MAF if the injectors are running that high % duty cycle.

Basically, the way I understand it is that the ECU has a table for the MAF that converts a hz reading to "airflow" which is then used in AFR calculations etc. Once it peaks on that table, it stays locked at that last value. I can't remember if it starts going leaner or richer afterwards, I'll have to check my logs again. Will hazard a guess at rich =P I still don't fully grasp the concept behind halving the MAF scale, as it seems that table in the ECU tops out at 1600hz anyway and MAF's are gerenally scaled to fit into that 0-1600hz window. I haven't looked closely enough at the stock ECU/MAF code etc. but it may even be something as simple as Mitsu scaling the stock VR4 to just below that 1600Hz barrier then making that last value in the table stupidly rich, so that if you modified/messed with the car (or god forbid, something actually go wrong =P) it would still be "safe" past that mark.
 
Is the fpr a rising rate one (1:1)?
Considering a stock vr4 can run 14 psi before hitting boost cut, there is no reason why your injectors and maf should be close to maxing out. Compression ration will not affect that. Low fuel pressure could explain the injector duty cycles and air leas could explain the high maf readings.
Really though, until you can tell what the afr's are doing under full load, you don't know if you are running stupidly rich (air leak) or dangerously lean (not enough fuel).
 
omad said:
What VR4 ECU are you using? Are the pins correct? (there's some pin swapping business that usually goes on between the AU and JAP models, may apply to you ?)
Do you have any datalogs that you can send/convert etc? Doing a log at WOT would be helpful at indicating what could be causing the lack of power.
Unless you have a modified chip in the ECU, 1600Hz will come up pretty quick. Most chips have the MAF Hz shown on the logger halved so it will display >1600hz (just double whatever is shown).
Are you using stock VR4 or GSR FPR? (is there a difference?)
There is a possibility you could be overruning the MAF if the injectors are running that high % duty cycle.

Basically, the way I understand it is that the ECU has a table for the MAF that converts a hz reading to "airflow" which is then used in AFR calculations etc. Once it peaks on that table, it stays locked at that last value. I can't remember if it starts going leaner or richer afterwards, I'll have to check my logs again. Will hazard a guess at rich =P I still don't fully grasp the concept behind halving the MAF scale, as it seems that table in the ECU tops out at 1600hz anyway and MAF's are gerenally scaled to fit into that 0-1600hz window. I haven't looked closely enough at the stock ECU/MAF code etc. but it may even be something as simple as Mitsu scaling the stock VR4 to just below that 1600Hz barrier then making that last value in the table stupidly rich, so that if you modified/messed with the car (or god forbid, something actually go wrong =P) it would still be "safe" past that mark.
Click to expand...

running stock Aspec ECU with matching MAF (came from same car) and i checked the pins before going turbo, there was no need for change..

i have the logs on an old Palm Pilot which wont connect to my comp any more.. dont know why.. but i'll see if i can post up..

and from what i can see and smell, after 1600hz, it literaly dumps fuel but power still cuts...

rob323 said:
Is the fpr a rising rate one (1:1)?
Considering a stock vr4 can run 14 psi before hitting boost cut, there is no reason why your injectors and maf should be close to maxing out. Compression ration will not affect that. Low fuel pressure could explain the injector duty cycles and air leas could explain the high maf readings.
Really though, until you can tell what the afr's are doing under full load, you don't know if you are running stupidly rich (air leak) or dangerously lean (not enough fuel).
Click to expand...

the Malpassi was a rising rate, but now on stock one..

i have a gauge for my fuel pressure in my car and the stock FPR raises the fuel up to 45psi during hard boost boost (i dont have the stock cut off valve for the FPR controlled via ECU)

ironically though i still get 10Lt/100km........

it may be time to go full after market ey.....

just thinking about it, the ECU was built to run off a stock low comp engine with a 14B, i'm now on high comp and a quick spool 16G, the amount of air flowing in and out of my current engine would be a hell of alot more then stock.... but i see where you both are coming from... i believe i need to invest in a Wide Band Asap.....

and just for visualization sake.. set up looks like this....
IMAG0271-2.jpg
 
JayRome said:
running stock Aspec ECU with matching MAF (came from same car) and i checked the pins before going turbo, there was no need for change..

i have the logs on an old Palm Pilot which wont connect to my comp any more.. dont know why.. but i'll see if i can post up..

and from what i can see and smell, after 1600hz, it literaly dumps fuel but power still cuts...



the Malpassi was a rising rate, but now on stock one..

i have a gauge for my fuel pressure in my car and the stock FPR raises the fuel up to 45psi during hard boost boost (i dont have the stock cut off valve for the FPR controlled via ECU)

ironically though i still get 10Lt/100km........

it may be time to go full after market ey.....

just thinking about it, the ECU was built to run off a stock low comp engine with a 14B, i'm now on high comp and a quick spool 16G, the amount of air flowing in and out of my current engine would be a hell of alot more then stock.... but i see where you both are coming from... i believe i need to invest in a Wide Band Asap.....

and just for visualization sake.. set up looks like this....
IMAG0271-2.jpg
Click to expand...

Just a quick one as I'm just about to head out, but fuel pressure should be approx 38-39 psi with the vac line off (from memory) at idle. May be more if you have an after market pump... actually that's a point.. what fuel pump are you running?

Also, don't need to aftermarket, ecmlink will sort you out. And yes, invest in a wb asap =) They're only ~$250ish to your door, maybe less now with the way the USD is. Innovate LC1 (i think that's the one) is the go man. ecmlink also has the capability to input and log wideband through the ECU.
 
omad said:
Just a quick one as I'm just about to head out, but fuel pressure should be approx 38-39 psi with the vac line off (from memory) at idle. May be more if you have an after market pump... actually that's a point.. what fuel pump are you running?

Also, don't need to aftermarket, ecmlink will sort you out. And yes, invest in a wb asap =) They're only ~$250ish to your door, maybe less now with the way the USD is. Innovate LC1 (i think that's the one) is the go man. ecmlink also has the capability to input and log wideband through the ECU.
Click to expand...

running a walbro intank pump... and yes base pressure is around 40psi....
 
Do the intake leak test as per VFAQ. Almost guarantee the TB will be pissing out air. The N/A tb seals are the wrong way around and only made to deal with vacuum and not internal pressure (boost). You'll either have to swap the seals and/or the TB. I'll try and draw a pretty picture in paint re: seals later when I have more time. You may also find a few other leaks here and there.
 

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