why cant i get to 100% throttle?

[Brados]

Bit of a noob question, but i cant seem to find the answer.

My PCM seems to be limiting my throttle a lot, sometimes it wont let it over 60%, others times i get as high as 79-80%. Ive Never had it over 80% or over 230-240g/s. Im getting aslmost 900mgc in the upper revs but lower in the revs its only 700ish, yet it dosnt open the throttle anymore.

Im pretty sure the issue is cylair but how you know you have hit cylair? What happens when you do hit cylair?

Also when go i full throttle instantly, on the logs it shows it has only gradually opened in stages. Is their a way around this or is it another limitation?

Car details: VY flash pcm, L67 (3.2 pulley 12psi),XP Cam, exhaust, headword and Extractors.

[Holden202T]

the only thing limiting your throttle would be the pedal/cable, if its getting 100% then i'd say you have a faulty TPS sensor maybe ?

[Brados]

Cheers for the help, I tried loging and manualy opening the throttle all the way in a few quick bursts while idling, Logs show it got to 99% throttle so their is nothing physically stoping it.

[Holden202T]

just so you know you can actually do that same test with the ignition on but don't need to have the engine running, makes it easier

[darcy]

...
Im pretty sure the issue is cylair but how you know you have hit cylair? What happens when you do hit cylair?
...
Car details: VY flash pcm, L67 (3.2 pulley 12psi),XP Cam, exhaust, headword and Extractors.

What do you mean by "hit cylair"?

Is this a NA car converted to L67?

[Brados]

Yeah it is a NA car with a L67 put in it. I thought their is a limit the pcm can handle of 300 g/s or 1000 mgc, people seemed to call it cylair.

[charlay86]

cylair/cylair50 is the cylinder airmass variable that the PCM uses for lookups, the PCM can calculate fueling above that limit, but you can't control the spark once you reach the 850mg of air per cylinder (or 1000mg/cyl, the variable used is selectable) limit.
The other issue is when you reach the limit of the MAF lookup tables, the PCM can't calculate any higher airflow once it reaches that limit.
The1 has addressed these problems in his extended bins.
Neither of those things will make your TPS behave erratically.

[Brados]

cylair/cylair50 is the cylinder airmass variable that the PCM uses for lookups, the PCM can calculate fueling above that limit, but you can't control the spark once you reach the 850mg of air per cylinder (or 1000mg/cyl, the variable used is selectable) limit.
The other issue is when you reach the limit of the MAF lookup tables, the PCM can't calculate any higher airflow once it reaches that limit.
The1 has addressed these problems in his extended bins.
Neither of those things will make your TPS behave erratically.

Thanks for that info! Really helps.

The TPS isn't erratic, the ecu just seems to be limiting throttle for some reason.


Im going to try a LS1 maf and LS1 throttlebody soon with extended bins and see if that changes it at all.

[darcy]

The TPS isn't erratic, the ecu just seems to be limiting throttle for some reason.

The ecu can't limit throttle opening.

If it's not reading 100% when you have pulled the blade wide open then there is an issue with the TPS.

[yoda69]

The ECU cannot limit throttle on a cable driven throttle body.
If you are not getting 100% check that floor mats (don't laugh, it happens often) are not limiting throttle travel.
If all ok, what is the TPS voltage at 0% throttle.
Can you get 100% moving throttle body by hand?