vader1

I hate to keep coming back. Went to street tune with the tuner for the third time. He is trying to help and was very good about it but it still has a wierd problem.


The roots TVS blower I think has a unique feature, (I am not sure if other blowers have this) that the air flows at cruising speeds through a bypass, and when throttle is applied, an actuator closes the bypass and routes air through the impellers of the blower.

My car was running really rich in light throttle condiditions on the freeway. And specifically cruising rpm's (3000-3500) when you were on a flat surface and then just get the slight incline and some load occurs where VERY light throttle is applied to maintain speed either with your foot or by the cruise control and in 6th gear, the car would go to the high 10's AFR, mild buck, sputter and stink. Street tuned with tuner and now that works fine in 6th on the freeway. Same exact area of the map but in lower gears (3-5) cruising on slower roads, same rpm range is now in the 16's to high 17's. What fixed richness in sixth is causing lean in other gears. I have no idea why gear would matter. Anything as high as about 15.5 does not scare me under light load and no boost, but above that scares me. I have read lots of newer gm's will cruise in the 15's from the factory now.

What I think this is caused by is this light load is where the blower is switching from the bypass to boost, and is maybe stuck somewhere in between because throttle is so low that is it starting to close the bypass. When this occurs, the tuner said "you are getting some really funky vacuum right now". He did not know how to make one problem go away (rich in sixth) and keep the other from appearing (lean in others) or vice versa.

This was never a problem with the piggyback because either the stock ecu was really well programmed or the Emanage did a good job compensating. It had target AFR's and would vary fuel to stay in a sane range. The Haltech has a very similar target AFR table given vaccum/boost and rpm, but it is not compensating and fixing these lean condidtions. When the tuner would go to the injector time fine tuing table to lean out the rich cell it creates the lean condition in the other gears. I have a basic understanding of what each table is doing and you can see the cursor flutter around the cells on the table where the engine is operating but I have no idea why it is NOT compensating and hitting the fuel targets it is supposed to.

I also understand that this transition from bypass to the blower creates wierd vacuum conditions, but it was fine with stock ecu/emanage and tons of OEM manufactures use these blowers and achieve perfect fueling. I am not understanding why the Haltech is not compensating and adjusting to meet the specified target in the map. This is just for a tiny "hole" in the map where this occurs, light load conditions in the 3000-3500 range. Any decent amount of throttle will snap the bypass shut and run normally, but the transition is causing problems. I want to be able to use the cruise control or cruise smoothly with my foot and not have to snap on and off throttle. I guess I should also mention the only other new thing in the equation is that before it used either stock map or Greddy sensor, now using internal MAP in the Haltech unit itself which is supposed to be a good sensor. I don't think there is anything wrong with it, it is showing boost and vacuum and I would guess there is a wierd spot where it transitions and is to be expected.

Lastly, how worried should I be about the car with no boost and very light load running for several seconds at a time in the 16-17.8 AFR range? I do not hear any knock but know that that lean is probably not good.

s2000Junky

All Superchargers work this way, roots or centrifugal. There is a bypass valve that vents the sc charge when cruising in vac. The spring rate of the bov determines when it will close and begin to pressurize the manifold. You either need to play with the spring rate and alter when you see boost at a particular load point (making sure boost is in open loop only and not fighting a closed loop operation which it sounds like it could be) or tune around it such as honing in on the trouble cell areas and changing the map table there to be more fine, so you can hopefully broaden and then pinpoint the problem cell area and rectify it. If the resolution isnt finite enough in that problem area, then one fuel cell will effect multiple load situations like you are experiencing. Also you may need to alter when open and closed loop transitions. But your tuner should know all of this and have tried one or all the above to zero in on it and make work. Im not a Haltec tuner, I tune my own emanage, but regardless of the device, they should all be strategize in a similar way.

Id check out my first suggestion of bov spring/opening rate and ECU open/closed loop transition load/throttle position timing to make sure these are all working together first. Then go from there.

vader1

Thanks for the pointers Junky.

My actuator in not adjustable so I will have to look at the tune. It is a sealed bulby thing with a diapragm inside that is pulled closed with vacuum but I don't see any way to adjust it. Should I be worried about the 16's and 17's for a few full seconds here and there under no boost/mild load in the mean time?

s2000Junky

You may end up needing a different adjustble BOV to replace if all else fails, just so you have another avenue to take in hopefully rectifying the problem by altering when boost starts to come in, either earlier or later then it currently is. Most have a spring you can change out, or even a pre load option on the BOV itself for some adjustbilty. Since it doesnt sound like yours has any of these features, it may be later on the list to try before checking/altering open/closed loop transition and or changing to a higher resolution on your fuel table to pinpoint which cell to tune without effecting the broader part of your map as it is sounding.

As long as its how you describe, I wouldn’t consider that type of lean condition an emergency, but its not ideal and I would still want to deal with it eventually. Keep tabs on it in the meantime. Do you have a boost gauge reference on the dash so you can see exactly at what load point in vac it does this? This can help you cross reference to see if its in open or closed loop part of the tune, or right at the cross over point.

vader1

The actuator actually works VERY quickly if you have any reasonable amount of throttle. It is fairly instantaeous. I think what is going on is the throttle application where I am experiencing it either by my foot or the cruise control is about 2-3% throttle. Extremely minimal. A tiny push more and the bypass snaps shut instantly and everything is fine, but these super minimal throttle inputs starts the actuator and it is probably half bypass, half through the blower and probably flutters. The tiny amount of throttle is not enough to push it the rest of the way and it still has some minimal load so it does not back to fully open either. Any decent amount of load induces enough throttle from me or the cruise to keep normal conditions but this is happening on pretty flat, very minor grades that one would see quite regularly cruising on what you generally consider a flat road.

My main concern since this tuner did not go into any discussion of open v closed loop, just tried to change a couple cells and shrugged a little bit at the prospect that fixing rich here made lean there. Or fixing lean here made rich there. But I am having my exhaust modified and going back for more fine tuning. Since he kind of seemed puzzled by the issue, I am wondering if I should go back to him or have the next round done somewhere else. He was trying to make time for the street tuning, but he was busy and had other appointments coming in. He is pretty well thought of and recommended though and seems to know Haltech well because his shop sells it. And wondering if I can limp a couple weeks with that light load leaness and use the throttle to stay out of that condition or if I need to worry it will grenade before I get back to the shop.

s2000Junky

The actuator actually works VERY quickly if you have any reasonable amount of throttle. It is fairly instantaeous. I think what is going on is the throttle application where I am experiencing it either by my foot or the cruise control is about 2-3% throttle. Extremely minimal. A tiny push more and the bypass snaps shut instantly and everything is fine, but these super minimal throttle inputs starts the actuator and it is probably half bypass, half through the blower and probably flutters. The tiny amount of throttle is not enough to push it the rest of the way and it still has some minimal load so it does not back to fully open either. Any decent amount of load induces enough throttle from me or the cruise to keep normal conditions but this is happening on pretty flat, very minor grades that one would see quite regularly cruising on what you generally consider a flat road.

My main concern since this tuner did not go into any discussion of open v closed loop, just tried to change a couple cells and shrugged a little bit at the prospect that fixing rich here made lean there. Or fixing lean here made rich there. But I am having my exhaust modified and going back for more fine tuning. Since he kind of seemed puzzled by the issue, I am wondering if I should go back to him or have the next round done somewhere else. He was trying to make time for the street tuning, but he was busy and had other appointments coming in. He is pretty well thought of and recommended though and seems to know Haltech well because his shop sells it. And wondering if I can limp a couple weeks with that light load leaness and use the throttle to stay out of that condition or if I need to worry it will grenade before I get back to the shop.
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Since the load is so light, I wouldn’t worry about driving it as is for now. He should be able to fix this issue if he is half as good as he is supposed to be.

vader1

Just had a random thought. I wonder if the car, when in open loop is not reading small transitions in throttle position sensor???? It has to be calibrated with this kit. But I guess that would explain the tiniest of throttle application in open loop, more air rushing in but the computer does not know throttle changed so it does not add any fuel? I dunno, just grasping at straws.

BuggyofMildDiscomfort

The MAP should pick that up though, what does the throttle transient table look like?

vader1

You went way over my head with that one.

s2000Junky

This is where the option of simply raising the threshold of when closed/open loop transitions could possibly do the trick. If the BOV is closing a bit prematurely for the current scaling then conflicts like this can happen. You should be in open loop just before you start seeing boost.