Thread: Think I went with too big of a turbo...

Ashton, TP stands for Theoretical Pulsewidth, it is the engine load in laymans terms.... I like this description more though.


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Yah, except this part is not actually true.Higher TP does mean there is an increased need for fuel, because it correlates to torque output. But higher TP does not mean higher load. And conversely, lower TP does not mean lower load. =(
If you keep load the same (for example, 100, or 200 kPa across the rev range), TP will rise and fall like it has no relation to load at all. Because it doesn't.

The best way I've found to describe TP is this...
In theory, if you log TP on any engine, it will match the torque curve almost exactly (ignoring scale). And because of that, it also matches the instantaneous fueling needs almost exactly. AKA, injector pulsewidth needed.
So when you do a typical 3rd gear pull, TP will rise with torque, peak, and then fall again toward redline in most cases.
It is fucking obnoxious to tune with.

Ben, is load, on a real ecu, considered the amount of air flowing?

That seems more accurate. It corresponds to airflow basicly. Like ben said you can have the same load on the engine but a higher rpm and the higher rpm is gonna require more fuel as there is a higher airflow.

If we would have had the tuner code out when the realtime ecus first came out I would have known that. lol. Makes perfect sense though. Easy enough.

He is running a 60-1 with a .63 back.

How is that untrue. Tp is directly related to load is it not?

60-1 is a much larger turbo. With a big turbine. This is the only reason I see 400+whp being made with a log manifold.

My friend had a 60-1 on his G20 and it made 420whp on 13psi with a tubular manifold.

The T31 turbine is small. Couple that with a log manifold and a .63 housing... you will get reversion.

I doubt the engine will make over 275whp on 15psi. And the only thing wrong is the reversion. Motor could be perfectly healthy. But that engine cannot breathe!

am using a protech log mani i made 377awhp i fine my car is very responsive but my tuner things the manifold is a bit restrictive

50 trim setup I have on my car made 36x at 17psi. I hqve a log mani with an old turbonetics 50 trim. Small turbo even for a de. Fyi.

No. Not in a set amount of time.

At WOT on an N/A engine at 1,000 rpm you are at full load. The cylinder will fill as best it can. At this low rpm, it can even be considered "lugging" the engine. However, air flow measured will be relatively low.

At WOT on an N/A engine at 6,000 rpm you are still at full load. The cylinder will fill as best it can. At this rpm air flow measured will be relatively high.

Both are at at the same "load" though.



With a MAF sensor, you can measure actual mass air flow. There really is no concept of measured or calculated "load" in a mass air flow setup. None whatsoever.

With a MAP+IAT sensor you have to guess at air flow using speed-density calculations and that is where load comes in. "Load" is simply an attempt at measuring the mass of the air entering the cylinder using pressure and temperature. This can either be used directly to index into a fuel map, or a more complicated speed-density calculation can be used to incorporate engine speed, cam profiles, estimated exhaust reversion, and other factors into the mix ultimately resulting in a Volumetric Efficiency result.

No, it is not.
Load is a term reserved for speed-density systems. It has no corollary in mass-air-flow systems (unless you want to ignorantly call TP "load" when it is not). There really is no comparing the two. Load is pressure (with temp correction). TP is exactly that. Theoretical Pulsewidth. A calculated guess as to what pulsewidth the injector needs to provide the required fuel. It takes a lot of things into account, mainly consisting of measured mass air flow and engine rpm although there are also look-up tables and funky constants in the mix.


I'm going to find some logs of TP and you'll get the idea.