Questions about engine load vs throttle position

s300 and SManager software questions & answers
Post Reply
originaldroidster
Posts: 8
Joined: Fri Jul 27, 2018 11:35 pm

Questions about engine load vs throttle position

Post by originaldroidster » Wed May 01, 2019 1:13 pm

I have a question that came to mind earlier when I was driving around and checking out engine load at different throttle openings, gears, inclines etc via map readings.

I noticed on some hills and different gears that sometimes the engine load (vacuum reading) can be the same at different throttle openings.

For example lets say a map reading of -17hg at 15% throtte vs -17hg at 25% is reached at different times how would afr stay consistent in open loop as the larger throttle opening brings in more air but it's still using the lookup table?

From what I've read and understand the tps is not part of the fuel calculation and only used for throttle tip in, fuel overrun, wot detection etc.

User avatar
Spunkster
Site Admin
Posts: 17933
Joined: Fri Sep 20, 2002 5:06 pm
Location: Hondata
Contact:

Re: Questions about engine load vs throttle position

Post by Spunkster » Wed May 01, 2019 2:19 pm

It is always using the tables. TPS is only used in certain conditions and is not part of measuring load.

originaldroidster
Posts: 8
Joined: Fri Jul 27, 2018 11:35 pm

Re: Questions about engine load vs throttle position

Post by originaldroidster » Wed May 01, 2019 2:45 pm

Ok so that is what I thought in regards to the tps.


So if same vacuum reading is achieved at different throttle positions under different conditions, the condition with the larger throttle opening would be putting more air into the cylinder therefore need more fuel to reach the same afr, yet it would be pulling fuel calculations from the same load cell for both throttle openings.


This is just a curious question I had, everything with my setup is working correctly. I just happened to be driving around partial throttle and I notice there was few times I was in same load range with different throttle openings. I may just be over thinking it to much, or maybe i read the map data wrong.

Thanks again.

crluver123
Posts: 117
Joined: Tue Oct 10, 2006 10:13 pm

Re: Questions about engine load vs throttle position

Post by crluver123 » Sun May 05, 2019 1:50 pm

fuel delivery at steady state is only according to RPM and the density of the air. manifold pressure = air density.
The reason you're getting the same manifold pressure at different throttle positions is because it's at different rpm's; the volumetric efficiency is different. It can also occur in very small variations according to the actual load on the engine. IE: going downhill in second gear vs going uphill in fourth gear.

But again, the only things that matter at steady state are the air density (manifold pressure) and RPM.

Post Reply