Nistune Forums

I currently have 2 cars in my workshop today that Im having similar issues with. One is a stock rb25 and the other is a stock rb20.

They have issues with hesitation.

I believe the issue to be knock sensor related but im not 100% convinced.

The latest version of nistune has a new variable called "TP Load Limit 2" with a default value of 64. The car im focussing on now (rb25) drives fine untill it reaches a load index of 64 or above. It will hapilly use higher values but the car starts chugging beyond 64. It doesn't miss fire it just looses all its go and struggles to rev. It feels like its pulling all the timing out but output display tells me its following the map correctly. When it hesitates, the knock maps are not highlighted but I notice that TP Load Limit 2 is highlighted.

Under what condition does the ecu deem its a good idea to use that value and why can't I find what makes it loose its power? Ignition and fuel outputs (according to the display) remain unaltered.

conditions under TP Load Limit 2 is highlighted

When the values of either TP load tables are exceeded by TP read in via consult the table will be highlighted red as per your screenshot.

Now as for the value, in the HCR32 code there are two safety cuts:

REV_LIMIT_SAFETY,&H7FE9,1,1,1,50,Rev Limit (safety cut - fuel)
AF_LIMIT2,&H7EEA,1,1,1,1,TP safety limit (safety cut - fuel)

These get used when the vehicle speed = 0 and Rev Limit > 6050 or TP > 64

You must not be having a speed signal on these vehicles going to the ECU if its cutting on the TP condition

In your screenshot I can see the speedo is zero whilst everything else is fine. Investigate the wire from the speedo cluster to the ECU as I dont think it is connected.

Created a new variable 'TP safety limit' which will show up in the rev limiters that contains this parameter. This will be in the 0.10.6 version

thanks for the reply's matt. sorry i didn't read it again till now.

Turns out the car had a dead fuel pump. its was just leaning out and it was a coincidence that it happened around a tp of 64.

no that car has no speed sensor wire hooked up. 60% of the cars i've tuned haven't. its never given me any trouble.

moral of the story is, i changed the fuel pump, tuned it, went great!

Usually ends up being a mechanical gremblin. Just trying to find it is half the issue

This is probably an old thread but hopefully Decs is subsribed to it...

Beware the cars with speed sensor disconnected. They will run fine most of the time. The problem only shows itself when they are run at full throttle, high load for extended periods - when they will hard cut. Many owners will never know - it's only the guys who really hammer their cars. I've had it happen mostly on Clubmans and racing buggies. The buggy guys hold them at WOT sometimes for minutes at a time. Had one drift guy too. He was actually happy that he was hitting the cut because it meant he was keeping the throttle wide open for longer!

Engines I've seen affected are mostly SR20DE (S13, 14,15). Only the DE's - DET's don't care. And RB20DET. But I'm sure there are others. Most will go for 6 to 10 seconds at WOT in 3rd gear or higher before they cut. Then normal operation resumes once rpm drops below a certain level (usually about 4500).

Pete L