Aurora 4.0l / Izuzu 5 speed swap into 88 coupe (Page 96/102)
cptsnoopy MAY 17, 12:23 AM
Went for a nice drive with 3 other Fiero's today. 127 miles round trip. The stumble is almost gone. There are a few more things to try to get rid of it all together and I am confident it will be good once I get a chance to play with some more. I really like how it drives and also, how it sounds. My wife is very happy with it too.
It is still running a little rich and it only averaged 19.8 mph for the trip. I am curious to see how much that can be improved over time.

Here are some pics of Myra's brother Greg getting a quick ride and one of us at the Rock Springs Cafe.

Charlie







[This message has been edited by cptsnoopy (edited 05-17-2015).]

cptsnoopy MAY 18, 05:11 PM
Due to the ITB's and the difficulty getting an accurate manifold air pressure, I'm going to try a tune using Alpha-N. Should be interesting, but not sure if it's the best option.

Charlie
eph_kay MAY 18, 08:20 PM

quote
Originally posted by cptsnoopy:

Due to the ITB's and the difficulty getting an accurate manifold air pressure, I'm going to try a tune using Alpha-N. Should be interesting, but not sure if it's the best option.

Charlie




Ill pitch in here

I have a vw rabbit with a vr6 swap that I turbo charged and made a custom ITB intake, I hold about 5-10inHg of vacuum depending on the day, and sadly couldn't use alpha-N because of the turbo, so I build the car with a MAF sensor and have been using megasquirt to control it, and it has a feature to use a VE table to act as a "trim table" to help add a load factor in. ITBs with boost are a pain to tune, and although most stand alones suck at MAF control I am very happy I did it on my car

So in other words, I think you will have good luck with your alpha-n and hopefully there is some ability to do some trim tables based on load.

Megasquirt actually has an ITB mode, which ofcouse you can't use with boost. But it runs alpha-n down low and shifts to SD based on a table, including a calibratable blend area.

Chris
cptsnoopy MAY 18, 08:34 PM
Thank you for the info Chris. The Dominator allows for Alpha-N idle and SD off idle but I'm not sure if a true hybrid is available with it. I'll play with it a bit and see how it goes.

Charlie
eph_kay MAY 18, 08:44 PM

quote
Originally posted by cptsnoopy:

Thank you for the info Chris. The Dominator allows for Alpha-N idle and SD off idle but I'm not sure if a true hybrid is available with it. I'll play with it a bit and see how it goes.

Charlie



I haven't quite followed your thread enough, other than drooling over the itbs

Where was the stumble happening?

I was have a huge lean spike and crazy stumble on initial throttle trying to get rolling from a start, and one of the things I was able to do was a setting they called wall wetting. Its a form of acceleration enrichment that basically works of the idea that some of the fuel from a itb set up sticks to the wall worse than a high vacuum stock set up, and requires adding more fuel on initial tip in. It helped a lot with my car

Chris
cptsnoopy MAY 18, 10:34 PM

quote
Originally posted by eph_kay:


I haven't quite followed your thread enough, other than drooling over the itbs

Where was the stumble happening?

I was have a huge lean spike and crazy stumble on initial throttle trying to get rolling from a start, and one of the things I was able to do was a setting they called wall wetting. Its a form of acceleration enrichment that basically works of the idea that some of the fuel from a itb set up sticks to the wall worse than a high vacuum stock set up, and requires adding more fuel on initial tip in. It helped a lot with my car

Chris

Yes, a tip in stumble both from idle and worse from shifting. The guy that put this ITB setup together had the vacuum issue and put check valves on 7 of the 8 vacuum ports and fed all 8 to an air chamber that had the MAP sensor mounted on it. It is a good workaround and the only issue I was having with that is that it would increase vacuum quickly when the throttle was closed but when the throttle was opened, the one vacuum port without a check valve was not enough to release the vacuum and it ramped up over several seconds. So the computer was thinking that the load was less than what was really happening and it would pick a point on the map that was much leaner than needed. Enriching the fuel map and increasing AE helped quite a bit to cover delay in vacuum change but I never took the time to try and fully tune it out. When I was looking at the data logs and saw what was happening, I decided to try removing another one of the check valves. all that did was reduce the vacuum from idle at 40Kpa to 50Kpa. I still need to look at the most recent data to see if the ramp up has gotten better or is the only effect not pulling as much vacuum. I might be in a situation where I just need to fine tune the ITB builder's solution to work better with my setup.

Charlie
eph_kay MAY 19, 01:48 PM
Oddly enough, since you are running speed density, you might set up like a blow off valve type thing that vents the vacuum right after a shift and then builds it back up.

This is just thinking out loud, I haven't thought all that through yet

On the other hand, I might put some check valves between my itb idle lines and my vacuum manifold to attempt to increase the vacuum seen at idle. I also run manual brakes so I don't need any vacuum, so I get to cheat a little

Chris
Will MAY 19, 03:44 PM

quote
Originally posted by cptsnoopy:
Yes, a tip in stumble both from idle and worse from shifting. The guy that put this ITB setup together had the vacuum issue and put check valves on 7 of the 8 vacuum ports and fed all 8 to an air chamber that had the MAP sensor mounted on it. It is a good workaround and the only issue I was having with that is that it would increase vacuum quickly when the throttle was closed but when the throttle was opened, the one vacuum port without a check valve was not enough to release the vacuum and it ramped up over several seconds. So the computer was thinking that the load was less than what was really happening and it would pick a point on the map that was much leaner than needed. Enriching the fuel map and increasing AE helped quite a bit to cover delay in vacuum change but I never took the time to try and fully tune it out. When I was looking at the data logs and saw what was happening, I decided to try removing another one of the check valves. all that did was reduce the vacuum from idle at 40Kpa to 50Kpa. I still need to look at the most recent data to see if the ramp up has gotten better or is the only effect not pulling as much vacuum. I might be in a situation where I just need to fine tune the ITB builder's solution to work better with my setup.

Charlie




Try ditching all the check valves. There's no danger in cross-talk among the throttles. OE's who use throttle per cylinder (mostly BMW) use fairly large connecting passages between the throttles for vacuum accessories... of course they also typically run MAF based engine management and not speed density.
cptsnoopy MAY 20, 02:45 PM

quote
Originally posted by Will:


Try ditching all the check valves. There's no danger in cross-talk among the throttles. OE's who use throttle per cylinder (mostly BMW) use fairly large connecting passages between the throttles for vacuum accessories... of course they also typically run MAF based engine management and not speed density.

I'm going to try Alpha-N tuning first then if I'm not happy with that, I'll try going back to SD and experimenting with the check valves.

Charlie
cptsnoopy MAY 21, 08:08 AM
Initial trials using Alpha-N backed with wbO2 compensation are very good. Much better than SD for drivability. I had a little issue with deceleration fuel cutoff when I first loaded the new changes from SD to AN so I left it turned off. I have some leaning to do in the higher rpm/low TPS areas of the map but other than that it should be ok. I'm not sure if I'll ever get any dyno numbers for it but I like how it drives. ~2750 rpm for 80mph in 5th gear. I'm guessing that I'll get around 20-22 mpg unless I lean the target AFR table for economy instead of performance.

I went ahead and capped off the 8 vacuum ports being used for the MAP sensor and pulled the 7 check valves and tubing out. The Holley has a baro sensor in the ecu but I left the MAP sensor plugged in reading ambient pressure just in case.

The high pressure a/c hardline ruptured under the car last night. It appears that there must've been some internal corrosion over the years. Now to decide on how to fix it. The a/c was working great up to that point.

Charlie

[This message has been edited by cptsnoopy (edited 05-21-2015).]