spinning tires on 1-2 shift causing to high of an RPM?

[starks]

my car was getting too high in rpms, much higher then usual / programmed for after a cam install, e85 and a pulley drop.

looking at the scan, it looks like it might be spinning the tires on the shift. it goes from 47mph to 53mph, then back to 47, 50, 57, 54,55,56. also getting about 1*kr at shifts but im pretty sure its just transmission noise. this scan is still the low boost pulley (3.3")

look around frame 648

[bilemke]

hmm. what car is this again?

Also, do you have the MPH values for shift lower then the RPM values? (RPM values set at the max RPM you want to see - roughly)

[Perforator]

That's happen to me before. I usually shift at 6200 but one time the tires spun a little between the shifts and I hit 6300 I think it was.

[starks]

its a 98 buick regal GS. VS cam, headers, e85 and a 3.3 pulley are the "major things" lots of other small things.


right now it has a 3.0 pulley im borrowing, and ill be buying a 2.9" (no kr with 3.0 running a little lean with 19.5* timming)

mph is set higher then RPM. 49mph, 5750rpm shifts. i did activate so that at 6300rpm it cuts timming to 5*. i had in a scan before it go up to 6360rpm...way to high.

[bilemke]

I personally set the MPH lower then engine speed. That way, the engine really can only rev as far as the engine rpm set for the shift.

If you run the math for the stock settings in out L67 w-bodies, I think you will see that GM did it this way too. Using the RPM value as the eventual final determination (MPH is hit before the RPM limit).

In your case, I imagine you normally hit 5750 before 49 mph. So, your engine is being allowed to spin much higher while your tires/wheels are spinning (the vss/pcm is probably not seeing 49 MPH until it is too late and the engine has hit a higher RPM then desired).

The above might help..

Also, a quick off topic question (well, sort of).... 65 lb injectors (approx)? Also, if you dont mind, know what sort of average MPG you are hitting?

Just curious because I have two custom PIDs I have been testing and I am curious how close they are on you car (when I was looking at your scan).

[starks]

thanks bilemke....ill give that a try, dropping the mph to 47, raising the shift to 5925 or so for now.

for my i havn't calculated yet, my DIC says 15 avg i think. but i dont think that can be accurate, running 65lb injectors and fuel cranked way up with e85. i havn't gone through a complete tank of gas, as i dont really drive this much in the winter

[bilemke]

Interesting.. Very interesting. If you catch the MPG on your next top off (based on actual gallons put in the tank), mind posting it up?

Also, thank you for confirming the injector size.. Confirms a Custom PID I have been working on.. I was able to use it to see the approximate injector size you were running by your scan.

[JerryH]

For a shift to occur, both MPH and RPM limits have to be set, however, this assumes a 0 delay time for the tranny to respond and shift... which only happens in never-never land due to tranny slippage, time to change gears, age, etc...

What needs to be done is you look at the average numbers and compensate.

IE: you set shift points to 6000 becuase you want 6000 RPM shifts, but you see it shifts at 6250. Setting nothing but your shift RPM to 5750, your tranny still takes the same time to complete the shift, so now you are hitting your desired 6000 RPM redline. If you do not change your MPH, but are exceeding them, thats fine... becuase remember, your tranny has to hit both RPM and MPH settings before the shift is commanded... so, even if you set MPH to 45MPH, and the shift occurs at 50MPH, its becuase the RPM limit was not touched.

Of course the whole thing could be reveresed (play with MPH and do not touch RPM)... but in general, unless you changed gears, I have never touched MPH on my car (they are at factory stock settings but I still exceed 6000 RPM on WOT shifts), I just played with the RPM settings and I am usually within 10-15 RPM of where I want it to be.

3 ways to do the same thing. Touch only MPH, touch only RPM or vary both to your taste. I do it the easy way and stick to the RPM to control WOT RPM shift points. I *do* use different MPH settings in the areas outside WOT, though.

[TDCRacing]

so for instance if you set the mph to 30 mph and the rpm that you desired to lets say 5925 then you would be seeing shifts at the rpm set(or a little above)...always...corect?



I still dont understand the point in the mph setting at all