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We have seen that behaviour on Dyno logs, and it seems like the blade only opens as much as it needs to maintain the required manifold pressure. We have seen the TPS at 60%-70% while the APP is at 100% but the MAP is near atmospheric so even if you had 100% opening it wouldn't be any higher on an NA engine. As the RPM's and MAF start going up the TB progressively starts to open the blade, at about 3000 rpms it gets to 100% and stays there. The MAP is always as high as it can be, this is what matters.
The 80's TPS at 100% APP is usually due to reading an SAE defined TPS, when you look at the right channel "generic TPS", it will be at 100% and read 100% too.
Very interesting thread. Tried to read many of the posts, but man, that's a lot to digest! So I will get right to it with my question:
Has anyone actually figured out how to get the throttle to open fully from a start (or near start). On my '17, Z06, A8, I can push the pedal all the way to the floor when starting off yet the throttle position won't hit 100% until I'm going about 30 something mph. I log every 1/4 mile run with my HP Tuners, so I'm confident this is the case. I have a new set of Hoosiers DR's and there's no wheel spin. I've heard several of you mention that it's possible, but which tables, parameters, etc are to be modified? If it's a trade secret, I will pay for the info. With the slow throttle response, I feel I'm leaving a little bit of 60' time on the table. I'm close to 1.6s, but with no wheel spin there must be a little bit of time reduction available. If only the throttle would open more quickly?
C'mon man, tell me how to do it.
Stock tune won't allow 100% throttle until 3200rpm. Easy change but requires a tune to do it
I am in for the answer also ... My throttle blade position is the same as yours at 85 % with the gas pedal to the floor .... I am sure there is a good reason but I cant think of it
Below is a screen shot of a 1st to 2nd gear pull , no nannies , everything off , you can clearly see that my throttle pedal is jammed to the floor but the , Throttle blade is at 85 %
Dave
Depending on which throttle position PID you are monitoring you will either see 83.9% for full throttle or 99.6% for full throttle. 83.9% on that PID is wide open
Attached picture shows it pretty well. The data shows the first couple seconds of a recent pass at the drag strip. It did take me a second or so to actually push the pedal all the way, but the throttle didn't hit 100% for quite a while later. I made a 1.75 s 60' time, even though throttle was pretty low most of that time. If only we could get the throttle to open a bit more quickly. You can also see no sign of wheel spin (vehicle speed increases steadily).
Thank you very much, John-6717. What I was trying to say on post #321, is that you won't get any more airflow/power when under 3-4k rpm even if the throttle were open 100%. Why? B/c the manifold pressure is as high as it can be and so is the airflow under those conditions. As you reach 4000 rpm then the throttle goes to 100%, because it is only then when you need that much opening to keep the manifold pressure at a maximum. Makes sense?
On the picture you can see some interesting things:
- When hit press the pedal at app. 0.6 sec., the throttle follows very fast, at app. 0,05 sec
- Although you continue to press the pedal further between 0.6 and 1.0 sec., the throttle opens a bit at first and then even goes back between app. 0,75 and 0,95 sec.
Either the torque management moved the plate, or it was just not that much throttle required to keep the manifold vacuum low, or ??
- Although the throttle moves within 0,05 sec, the engines needs 0.15 sec to start increasing rpm
On the picture you can see some interesting things:
- When hit press the pedal at app. 0.6 sec., the throttle follows very fast, at app. 0,05 sec
- Although you continue to press the pedal further between 0.6 and 1.0 sec., the throttle opens a bit at first and then even goes back between app. 0,75 and 0,95 sec.
Either the torque management moved the plate, or it was just not that much throttle required to keep the manifold vacuum low, or ??
- Although the throttle moves within 0,05 sec, the engines needs 0.15 sec to start increasing rpm
Regards
Götz
It'd be nice to see MAP on that plot. I think it is because there's not much throttle required to keep MAP at maximum. The throttle motor often overshoots a bit and corrects, that might also explain the little TP dip.
Thank you very much, John-6717. What I was trying to say on post #321, is that you won't get any more airflow/power when under 3-4k rpm even if the throttle were open 100%. Why? B/c the manifold pressure is as high as it can be and so is the airflow under those conditions. As you reach 4000 rpm then the throttle goes to 100%, because it is only then when you need that much opening to keep the manifold pressure at a maximum. Makes sense?
I can't say this makes any sense. Are you saying that the throttle will never open 100% until you get to about 4,000 RPM? Pretty sure this is not the case, but will confirm shortly. A full pedal push at low RPM in say 4th gear should show us. How can the manifold pressure be as high as it can be when I make more boost at higher RPM's?
I can't say this makes any sense. Are you saying that the throttle will never open 100% until you get to about 4,000 RPM? Pretty sure this is not the case, but will confirm shortly. A full pedal push at low RPM in say 4th gear should show us. How can the manifold pressure be as high as it can be when I make more boost at higher RPM's?
Changing the tune to allow the throttle to open 100% below 3200rpm DOES make a big difference compared to stock values. Especially when launching the car at the track etc.
I dont have my laptop with me but I believe its the Throttle % by rpm table. My 17 GS did not command 100% until 3200rpm and when we did the tune it went from barely wanting to spin from a stop to lighting the tires up. With the tune and boltons the car also hit 1.55 60fts on radials at the track leaving off idle
I can't say this makes any sense. Are you saying that the throttle will never open 100% until you get to about 4,000 RPM? Pretty sure this is not the case, but will confirm shortly. A full pedal push at low RPM in say 4th gear should show us. How can the manifold pressure be as high as it can be when I make more boost at higher RPM's?
Yes, that is what your plot shows. Actually, around 5000 rpms is when you reach 100% throttle. Since we didn't know whether you were NA or SC until now, I mentioned the example of a NA car in post #321. In your case, it would be the supercharger inlet what's downstream of the TB, not the manifold, that's assuming it is a PD supercharger.
When the MAP is as high as it can be for the current RPM's, you can open the throttle all you want and you won't get any more flow. The lower the RPM's the truer this is. Meaning after some amount opening the TB is not an obstruction, given RPM's and air density in the manifold, these last two set the flow, not the TB.
Look at this pull of a stock LT1. The cursor is at 3200 rpm and 100% throttle (SAE TP% is 84%). Now look to the left of the cursor and see that the MAP was already 100 kpa (101 is atmospheric). Did it matter that the throttle was at 60% under 3200 rpm? No. If you get to fully open the throttle on a NA car before 3200 rpm, and you get greater than 100 kpa in the manifold, it would be very interesting to see.
Last edited by Mike@SolerEngr; Oct 21, 2020 at 03:41 PM.
Oops, didn't realize I wasn't on the Z06 forum. Just searched the topic and ended up here. Here is a graph of a log I did this afternoon. It's 4th gear at relatively low RPM. Throttle actually beats the pedal to 100%.
Exactly, on this last plot you can see that when you are at ~1750 rpm and ~35% TP, you requested 100% and it only gave you ~70% TP, that was enough to raise and keep MAP, then it slowly kept opening to 85% TP @ 2750 rpm. Had it let you have 100% TP you would have seen the same MAP, so why do it? I think your TB is working as it should.
We are not against tuning, you can try it and see what happens. What I'm trying to explain is that opening the throttle to 100% is not the answer under certain driving conditions and that the control logic is doing what it should by not moving the blade any more than it should unnecessarily.
Comparing the three graphs I presented makes it pretty clear that it isn't a MAP issue at launch. If the throttle opens immediately to 100% in 4th gear at about 3,000 RPM, one would think it should do something similar in 1st gear. That's where I hope to get some benefit in making the throttle open a bit more quickly. Make sense?
There is a range of lower RPM's within which you will always find a value of opening <100% that works the same as 100%. If you make that value 100% and get one more drop of power, then GM got the ETC control logic wrong. Nannies off of course. Again, try it and see.
The throttle body is not a valve with unlimited potential at its source, where opening more always gives you more. One should look at it as a system limited by the displacement, the rpm's, and the air density setting a limited demand. When that demand is met without obstructions, opening more will not yield more than what it is demanded.
Last edited by Mike@SolerEngr; Oct 22, 2020 at 11:17 AM.
Reason: added signature
Mike
I saw in one of your posts that the trans type needs to be taken into consideration when ordering a TB
My car is a 2016 C7 Z51 A8
I bought the TB from Summit part # VRM-VR-TCR-C7
Air Intake Kit, VR TCR-7 Ram Air System, Black Plastic, Green Synthetic Filter, Chevrolet, Corvette C7, Kit
(Mfr. #: VR-TCR-C7)
I didnt get the pedal setup because I'm getting a tune after I install the TB and a CAI I got.
So is this the correct TB and will it have all the latest upgrades?
Thanks
Dan
Mike
I saw in one of your posts that the trans type needs to be taken into consideration when ordering a TB
My car is a 2016 C7 Z51 A8
I bought the TB from Summit part # VRM-VR-TCR-C7
Air Intake Kit, VR TCR-7 Ram Air System, Black Plastic, Green Synthetic Filter, Chevrolet, Corvette C7, Kit
(Mfr. #: VR-TCR-C7)
I didnt get the pedal setup because I'm getting a tune after I install the TB and a CAI I got.
So is this the correct TB and will it have all the latest upgrades?
Thanks
Dan
Thanks, Dan. The link you sent is for a CAI. Summit is not one of our dealers, so the TB you've got must be another brand. Anyway, the right TB from us would be PN SE8223-040, and yes we always ship our latest and greatest.
Also, no worries about our controller PN SE0820-TC and the tune, they can work together. The only thing is when loading the tune, uninstall the controller, then reinstall. Or simply wait until the tune is done.
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VRM-VR-TCR-C7