How much boost on a stock motor?
Registered User
Joined: Jul 2005
Posts: 1,670
Likes: 0
From: Gie
Originally Posted by spoiled@21,Nov 7 2005, 10:54 PM
One of the reasons that Honda and Toyota did so well there last two years making turbo 6s for cart was that developed a manifold that created airlow vortices in such a way that it would fool the "pop-off valve" (Cart tech speak for wastegate) that was league mandatory set to 14psi. Ford raised a big fuss about being slow and it was found that the Honda/Toyota motors actually boosted 15-15.2 psi. Since their designs were within regulation they had to change the pop off valve design to accomodate these new airflow patterns.
thus, placement of the wastegate on the manifold can negate some of the actual boost pressing against the wastegate spring by means of "laminar physics." I am not in a position to say that Tinker did this on purpose but seeing as it is not an equal length manifold it makes this happen much more easily. When all the tubes are not equal then there are 4 different airflows that are going to have 4 different "angles of attack" on the inner walls of the manifold just before the wastegate opening which creates turbulence in the airflow that can fool the wastegate. So is short, yes it is possible to create greater boost than the wastegate should theoretically allow.
So all that said in explaining creep you still have this turbulent air. The GT turbos are effecient enough and spin easily enough that the turbulent air spins then just as easily as clean air.
thus, placement of the wastegate on the manifold can negate some of the actual boost pressing against the wastegate spring by means of "laminar physics." I am not in a position to say that Tinker did this on purpose but seeing as it is not an equal length manifold it makes this happen much more easily. When all the tubes are not equal then there are 4 different airflows that are going to have 4 different "angles of attack" on the inner walls of the manifold just before the wastegate opening which creates turbulence in the airflow that can fool the wastegate. So is short, yes it is possible to create greater boost than the wastegate should theoretically allow.
So all that said in explaining creep you still have this turbulent air. The GT turbos are effecient enough and spin easily enough that the turbulent air spins then just as easily as clean air.
No one can truly tell what exactly goes on inside the manifold. It can be very accurately approximated though. I can definitely see how certain engine speed frequencies/combinations of manifold lengths and geometries could "fool" the wastegate. This works both ways as well. A high pressure zone could develop at the wastegate and cause it to vent, even though the pressure seen elsewhere may be less (as opposed to the case with the CART engines).
Turbomachinery kicks ass.
Registered User
Joined: Oct 2004
Posts: 697
Likes: 1
From: Traverse City, Michigan
Originally Posted by Scorpion,Nov 11 2005, 06:08 PM
Well right now I'm running 12 pounds at 17* timing with 0 knock. This is off a street tune. I'm going to get some dyno time in the next week and see how are I can push it.
With stock tires, my car would break traction from a roll-on in 2nd gear at 8-9psi. Another 3-4psi has to be killer 
Thread Starter
Registered User
Joined: Apr 2003
Posts: 1,848
Likes: 1
From: Riverview
To be honest I don't know...I've been in the passanger seat the whole time 
Last night the wife (that's right, she can drive with the best of them
) and I went out for some high boost tuning. I'm still having issues with the wastegate duty map in the EMS, but I think I figured it out, of course by the time I did it was like 3 in the morning we we where both way to tired to drive anymore. I'm going to fix my oil seal leak this morning then maybe get a few more tweaks done. The 17th I'm going to try and hit the 1320 here, and we'll see how much fast 12psi is to 8.
Last night the wife (that's right, she can drive with the best of them
) and I went out for some high boost tuning. I'm still having issues with the wastegate duty map in the EMS, but I think I figured it out, of course by the time I did it was like 3 in the morning we we where both way to tired to drive anymore. I'm going to fix my oil seal leak this morning then maybe get a few more tweaks done. The 17th I'm going to try and hit the 1320 here, and we'll see how much fast 12psi is to 8.
Registered User
Joined: Mar 2004
Posts: 2,976
Likes: 1
From: Slovakian living in Dubai
Excuse my ignorance but how do you guys street tune under boost?
How do you keep the map in the same fuel cell to tune it once boost hits in?My tuner can street tune only below boost, the rest on the dyno only?!?!?!?
How do you keep the map in the same fuel cell to tune it once boost hits in?My tuner can street tune only below boost, the rest on the dyno only?!?!?!?
Registered User
Joined: Oct 2004
Posts: 697
Likes: 1
From: Traverse City, Michigan
You open AEM PRO, connecto, then open the "Templates" tab, then the "Tuning" template. Push F6, and it datalogs everything you do until you push F6 again(this would be a good time to do a 3rd gear, WOT pull). You get done with the run, push F6, pull over, open AEM LOG and the file that was just created, and everything you want to see can be selected and displayed.
THEN you go back and tune each cell, based on the datalogging results. The AEM EMS is a WONDERFUL tuning tool
THEN you go back and tune each cell, based on the datalogging results. The AEM EMS is a WONDERFUL tuning tool
Registered User
Joined: Mar 2004
Posts: 2,976
Likes: 1
From: Slovakian living in Dubai
Cody but if I understand this right, you can do this only once the map is close to perfect right? Let me say EVERYTHING above 5000rpm is 2 poinst to lean and you floor it....you know what I mean? But thanks for telling me, I will try to get rid of the pre VTEC dip once my tuner has time on the street forst.Thanks again!
Thread
Thread Starter
Forum
Replies
Last Post