Balancing S38 ITBs

Specific conversations and info for the BMW E28 M5 and M535i.
HealeyBN7
Posts: 251
Joined: Feb 06, 2009 5:22 PM
Location: Thousand Oaks, CA

Re: Balancing S38 ITBs

Post by HealeyBN7 »

Thanks for the feedback Dave. Looks like you mastered it in short order and the results look great.

It doesn't fix all S38 problems (TPS actuation, ICV response, worn linkage or misalignments, valve clearances, etc), but if the basics are already covered, after tuning, the car should idle a bit more smoothly and if need be you can replace the rotten o-rings or any of the worn ITB components and re-tune to return to a stable flow.

Nice job on the videos! Thanks for linking them to the forum.

Dean
alim_h
Posts: 58
Joined: Mar 09, 2015 3:10 PM
Location: Albuquerque, NM

Re: Balancing S38 ITBs

Post by alim_h »

Hey Dean,

Fairly new to this board and the S38 world. Got the valves adjusted, new cap, new TPS, etc. Still idles rough and down on power. On to throttle syncing. Still loaning out the Mantimanometer? Would love to use it!

Also, when adjusting the butterfly closing gap, does the .01 refer to .01 in or .01 mm? I'm hoping inches otherwise the dial gauge i have doesn't read that fine!

Thanks!
milarsky
Posts: 515
Joined: Jan 26, 2013 11:19 AM
Location: NYC

Re: Balancing S38 ITBs

Post by milarsky »

Hello Alim!

So sorry we never got to meet in Santa Fe, but I will be back next summer.

Have you checked all the following baseline items:

-Coolant Temp Sensor
-Correct Spark plugs (gapped properly)
-Crankshaft/RPM sensor
-Fuel Pressure Regulator
-Oxygen Sensor
-Check for any vacuum leaks?


all best,
Jeff
alim_h
Posts: 58
Joined: Mar 09, 2015 3:10 PM
Location: Albuquerque, NM

Re: Balancing S38 ITBs

Post by alim_h »

Hey Jeff,

Next summer for sure!

Replaced Coolant Temp Sensor, Spark Plugs, and O2 sensor. Checked Crankshaft and Camshaft sensors, as well as FPR. I think I got most of the vacuum leaks. I can read 8 - 9 inHg of vacuum from the EGR port, so I think I should be ok there.

Comes down to AFM and/or throttle bodies now. Actually, I wish I could've swapped AFM's with you to see if that was the culprit. I will probably just do the MAF conversion now, though. I've only heard great things about it.
HealeyBN7
Posts: 251
Joined: Feb 06, 2009 5:22 PM
Location: Thousand Oaks, CA

Re: Balancing S38 ITBs

Post by HealeyBN7 »

alim_h wrote:Hey Dean,

Fairly new to this board and the S38 world. Got the valves adjusted, new cap, new TPS, etc. Still idles rough and down on power. On to throttle syncing. Still loaning out the Mantimanometer? Would love to use it!

Also, when adjusting the butterfly closing gap, does the .01 refer to .01 in or .01 mm? I'm hoping inches otherwise the dial gauge i have doesn't read that fine!

Thanks!
I would be happy to lend it to you. The gap is measured in inches.

Since you say that you are down on power, In don't think balancing the ITBs will make much difference. It could help with idle smoothness and transition off idle issues, but once the butterfies are partially cracked the bypass screws are no longer in play and any performance issues would come from somewhere else.

Before you balance the ITBs you should make sure your valves are properly adjusted. If you plan on doing that later it will impact the ITB adjustments.

Let me know when you want it sent over. We will need to exchange emails off line so you can paypal me for shipping and a small deposit. Also, if you don't need the dial indicator, all the better. Turns out it is now the only one I have:)

Dean
Nanajoth
Posts: 1551
Joined: Apr 19, 2008 6:38 PM
Location: TX

Re: Balancing S38 ITBs

Post by Nanajoth »

HealeyBN7 wrote:

Since you say that you are down on power, In don't think balancing the ITBs will make much difference. It could help with idle smoothness and transition off idle issues, but once the butterfies are partially cracked the bypass screws are no longer in play and any performance issues would come from somewhere else.



Dean
HealeyBN7 wrote:I reset the OBC MPG tracker before heading out to work this morning. 80 mile round trip. Mostly 80 MPH freeway on the way into work. Traffic on the way home. I haven't see this average before, except in the wife's '84 528e.

Now that's a measurable improvement even on crappy California summer gas blend.

Dean


So what you are saying is that this was due to a difference in your driving style and not your throttle adjustment, sounds misleading.
HealeyBN7
Posts: 251
Joined: Feb 06, 2009 5:22 PM
Location: Thousand Oaks, CA

Re: Balancing S38 ITBs

Post by HealeyBN7 »

Nanajoth wrote:
HealeyBN7 wrote:

Since you say that you are down on power, In don't think balancing the ITBs will make much difference. It could help with idle smoothness and transition off idle issues, but once the butterfies are partially cracked the bypass screws are no longer in play and any performance issues would come from somewhere else.



Dean
HealeyBN7 wrote:I reset the OBC MPG tracker before heading out to work this morning. 80 mile round trip. Mostly 80 MPH freeway on the way into work. Traffic on the way home. I haven't see this average before, except in the wife's '84 528e.

Now that's a measurable improvement even on crappy California summer gas blend.

Dean


So what you are saying is that this was due to a difference in your driving style and not your throttle adjustment, sounds misleading.
You are kidding, right? You took two sentences from this thread separated by seven months and re-ordered them, one as a self report, and the other in response to helping a fellow M5 owner that has an AFM issue and you drew the conclusion that I am trying to be misleading???

If there is something amiss about the process, method or tools described for balancing the ITBs please do share.

Dean
Nanajoth
Posts: 1551
Joined: Apr 19, 2008 6:38 PM
Location: TX

Re: Balancing S38 ITBs

Post by Nanajoth »

I am curious as to how you gained the extra MPG when you stated that adjusting the ITBs will not help you as far as performance goes and the bypass screws are no longer involved. It looks misleading when you state in the beginning of the thread that you gained all sorts of mileage and compare it to a 528e, then down the road say that this process will not help with performance issues. There is nothing wrong with your adjustment process.
HealeyBN7
Posts: 251
Joined: Feb 06, 2009 5:22 PM
Location: Thousand Oaks, CA

Re: Balancing S38 ITBs

Post by HealeyBN7 »

Nanajoth wrote:I am curious as to how you gained the extra MPG when you stated that adjusting the ITBs will not help you as far as performance goes and the bypass screws are no longer involved. It looks misleading when you state in the beginning of the thread that you gained all sorts of mileage and compare it to a 528e, then down the road say that this process will not help with performance issues. There is nothing wrong with your adjustment process.
I think the problem is confusion by the term "performance". I equate performance with power, torque and acceleration, not on idle or off idle efficiency/mileage. See if this helps.

On my M5 the ITBs were fairly far out of adjustment (both the butterflies and the bypass screws). The car struggled (surged) at very low freeway speeds and the ECU/LM2 indicated that it was hunting (...wasting gas). Returning the ITBs to their proper synchronization allowed for much smoother light throttle drive-ability and the resulting "OBC" mileage under ideal conditions. Unfortunately, I don't drive that way most of the time, but you could. If you have an S38 and use the right pedal then you know they are capable of returning you to the filling station in quick order. My mileage has been averaging 18.5-19.5.

The purpose of this thread was not to improve S38 mileage. That was just an observation to demonstrate that the ITBs are no longer "fighting" with each other. I was looking for a repeatable way to adjust the ITBs for on idle smoothness and help with an off idle transition step. The book method of moving the vacuum gauge from port to port was not returning repeatable results.

Regarding Alim's car, he is describing "performance issues" across the power band. Adjusting the ITBs at idle or just off idle really won't have any impact at all at full or part throttle. In off line discussions with Alim it sounds like he may have a bad AFM. I offered to loan him my spare AFM for testing. I recommended that he find the root cause of the "low on power" issue first before investing the in the time to fine tune the ITBs.

Dean
Nanajoth
Posts: 1551
Joined: Apr 19, 2008 6:38 PM
Location: TX

Re: Balancing S38 ITBs

Post by Nanajoth »

That makes sense, thank you for clarifying.
wjtesquire
Posts: 16
Joined: Aug 07, 2010 8:42 AM
Location: Charleston, SC

Re: Balancing S38 ITBs

Post by wjtesquire »

Wow! Dean was kind enough to share the Mantis Magic Manometer with me and look at the results:

Before:

https://www.youtube.com/watch?v=x91Dia4 ... load_owner

After 5 minutes of adjusting:

https://www.youtube.com/watch?v=nINNnME ... load_owner

I can't tell you how much smoother and more refined my car is running now. I will report back with the MPG data as soon as I can verify it. I highly recommend every S38/M88 owner use this tool. Huge improvements in idle and acceleration.
wkohler
Posts: 50921
Joined: Oct 05, 2006 11:04 PM
Location: Phönix, Arizona, USA
Contact:

Re: Balancing S38 ITBs

Post by wkohler »

Wow. That sounds smoother too!
tn535i
Posts: 5585
Joined: Jul 14, 2006 1:30 PM
Location: Middle Tennessee

Re: Balancing S38 ITBs

Post by tn535i »

My car will sound a bit like the first video if the idle is too low (700 ish) and more like the second at a slightly higher idle (900 ish). I wonder if the idle speed also came up before and after. The S38 is supposed to idle a little higher than most think it should based on other motors. But the balance (or lack of) is really apparent and much improved. I've done mine differently (2 at a time, many measurements/adjustments) but I'm due for a valve adjust and balance and I need to get set up like this.

Good stuff.
wjtesquire
Posts: 16
Joined: Aug 07, 2010 8:42 AM
Location: Charleston, SC

Re: Balancing S38 ITBs

Post by wjtesquire »

I had my idle set higher so it would not struggle when the ac compressor cycled on. With the compressor off, I would see the idle speeds of about 900 rpm. When the a/c compressor cycled on the RPM would dip to about 700. After sync I set the idle to 700 and it doesn't change when the a/c compressor cycles on.
tn535i
Posts: 5585
Joined: Jul 14, 2006 1:30 PM
Location: Middle Tennessee

Re: Balancing S38 ITBs

Post by tn535i »

That is really smooth then for 700 rpm. Nice. But I think BMW would say the idle speed on the S38 should be closer to 800-900 range. It also sounds like it is not dithering but the clip is only a few seconds. Did you look at the O2 output to see if it dithers from rich to lean every few seconds? If not you are supposed to adjust the AFM air bypass until it can dither.
wjtesquire
Posts: 16
Joined: Aug 07, 2010 8:42 AM
Location: Charleston, SC

Re: Balancing S38 ITBs

Post by wjtesquire »

I just calculated my fuel consumption over the last two tankfuls after using the manometer and averaged 16.6 miles per gallon. That is up from 14.3!
Bhart
Posts: 1
Joined: May 01, 2016 6:32 AM
Location: Ontario, Canada

Re: Balancing S38 ITBs

Post by Bhart »

Would a motorcycle synchronizing tool like the http://www.motionpro.com/product/08-0411 do a similar job as the MantisManometer?
HealeyBN7
Posts: 251
Joined: Feb 06, 2009 5:22 PM
Location: Thousand Oaks, CA

Re: Balancing S38 ITBs

Post by HealeyBN7 »

Bhart wrote:Would a motorcycle synchronizing tool like the http://www.motionpro.com/product/08-0411 do a similar job as the MantisManometer?
Yes, but you need six ports. Not many six cylinder bikes out there:)

Dean
tn535i
Posts: 5585
Joined: Jul 14, 2006 1:30 PM
Location: Middle Tennessee

Re: Balancing S38 ITBs

Post by tn535i »

I've done it with just two port manifold. Almost like using a vacuum gauge but you balance 5 to one master cylinder that you pick, #1 for example. You might have to go through a couple times but you can certainly get it quite good. You'll want some sort of restrictor to take the bounce out and you must be sure to clamp off any tube you remove or the fluid may get sucked out. ATF is good to use because it's easy to see, low viscosity, and if you suck it into the engine it shouldn't hurt anything.

The six port manifold is probably much better.
Randomg
Posts: 480
Joined: Jul 12, 2007 3:12 PM
Location: Seattle

Re: Balancing S38 ITBs

Post by Randomg »

Made my first attempt with the mantis this evening. Boy were my cylinders off. I was able to even them out with the cylinder screws, but it looks like I'm going to have to tweak some of the other variables to get it right, as my vacuum average isn't quite right, and my idle speed is quite high.

My valves are adjusted, I set my butterfly valves with a dial indicator and all are resting on the stopper, my adjustment screws have been cleaned out and the seals replaced, and all the rubber intake boots have been replaced. There aren't many places left to have an intake leak. I currently have my idle speed screw tightened all the way and my idle speed is still high with one of the individual cylinder screws tightened all the way down, so I'm at the limit of the screws adjustment range.

I'm thinking 3 variables are left: intake leak (either in something that affects all cylinder, or in the boot or few seals that each cylinder intake has), butterfly valves are adjusted wrong allowing too much air to go past them when they are closed, idle valve is malfunctioning (stuck fully open), or there is some ECU variable at work (the war chip does have a tab for idle speed). I have some investigation to do this week/weekend.
HealeyBN7
Posts: 251
Joined: Feb 06, 2009 5:22 PM
Location: Thousand Oaks, CA

Re: Balancing S38 ITBs

Post by HealeyBN7 »

Double check the butterfly gap specs. If you read back through the thread I think there was some confusion on how it was quoted in the instruction sheet. It is not clear enough.

The gap should be .1mm-.15mm. That's about .004in - .006in. Mine was happier on the "closed" side of the adjustment.

Here is a photo of the service manual.

Image

Sorry for any rework this caused you. I'll get the pdf updated.

Dean
Randomg
Posts: 480
Joined: Jul 12, 2007 3:12 PM
Location: Seattle

Re: Balancing S38 ITBs

Post by Randomg »

I had done the adjustment in the past, so I didn't use your part of the kit for it. I'll go through the butterfly adjustment again and hopefully that fixes it. If memory serves me, I already adjusted it to as closed as possible (I've had trouble getting my idle speed low enough since the rebuild), but I will try to do it more carefully with your tool. I think I'll just put them all at full closed (butterfly resting against the intake runner) to see if I can get the idle lower than 800 rpm to verify that there's not something else that also needs to happen to lower the idle to the right rpm. I'll try to do that tonight.
tn535i
Posts: 5585
Joined: Jul 14, 2006 1:30 PM
Location: Middle Tennessee

Re: Balancing S38 ITBs

Post by tn535i »

Have you checked your TPS to make sure it is sending the idle signal or even jumpered it on the harness side to force the signal. Does the War chip still have the provision to jumper the TPS input and put the computer in open loop mode without idle control. This is where you should be balancing everything anyway.

I'm not a fan of micrometer adjustment of the mechanical linkage. I would unplug the TPS to see where the default ICV position allows it to idle. If too high (>1000) I will close down the t/b's and sort of balance the t/b's with a gauge before fine tuning. I'll bet this is where you are right now. If you have adjusted the t/b's you'll loose it as soon as you tweak anything mechanical and have to repeat. So if that's the case just start over. I would set all the bypass screws about 1-1.5 turns open then balance the mechanical movement of the t/b's using a vac gauge and trying to hit about 900-1000 rpm on a warm engine with the TPS inputs bridged to run in open loop. Once the mechanical adjustment is about right you can proceed back through the individual adjustments. Then remove the jumper on the TPS harness and adjust the mixture on the AFM bypass to get slightly rich. Then re-adjust the TPS switch if needed and plug that back in. It should now be in idle control and dithering and you can use the big idle bypass screw to get the speed you want, but it should be about right.

If the t/b's are too far open the ICV will not close enough to bring the idle down and this may be where you are now.
If the t/b's are too far closed the ICV can't open enough to raise idle on a cold engine and keep it running right.
You need to be at the proper mid point in the ICV range or actually just above mid point with ICV slightly closed on a warm engine IMO.
I don't think you ever get there with measurement of the t/b's.
Randomg
Posts: 480
Joined: Jul 12, 2007 3:12 PM
Location: Seattle

Re: Balancing S38 ITBs

Post by Randomg »

My tps works, and I was doing the tuning with it jumpered. I think setting the bypass screws to the default position and using the butterfly stoppers isn't a bad idea to get it close, but another thing to keep in mind is that I'm not just adjusting idle here, ideally you want the throttles all in the same position so that at all other throttle positions are as closely matched as possible. I think the two goals with the mechanical linkage are that the butterflies don't rest against the intake wall (slowly wearing down the aluminum, or potentially binding and getting stuck), and setting them all to the same angle. If their resting angle is not to spec but you can get your idle rpm, afr, vacuum and wot angle correct, I think that's the way to go.

After writing the above I think my current plan is: set bypass screws and idle speed screw to default, adjust using the butterfly stoppers to get the vacuum readings as close as possible, then go in and measure the butterflies and try to set them to the average reading (so if 1-2 is .8, 3-4 is 1.1, and 5-6 is 1.2, I'll try to set them all to 1.03), then check WOT to make sure they're close at the other end of their range, and then use the bypass screws to fine tune. I think this should work assuming that I don't run into the limit of the bypass screw range (maybe I should start with more than 1 turn when doing the butterfly stopper adjustment), but it's possible that one of the intakes is worn so much that in same position as one of the other sets, it just lets too much air flow past the butterfly to let it stay at the same angle as the other two sets.
tn535i
Posts: 5585
Joined: Jul 14, 2006 1:30 PM
Location: Middle Tennessee

Re: Balancing S38 ITBs

Post by tn535i »

I think you have a good plan. Absolutely agree you don't want any of the throttle plates completely closed so checking that out is a good idea. I think if they were fully closed you would need to open the bypass screws way far though. I think the adjustments you'll be making won't make a whit's difference at WOT, maybe at cracked throttle. For that try using the manometer both at idle and with the throttles all just off idle slightly, maybe 1500 rpm or so with a load on it from A/C, and if all is well you should get good balance both ways. If not you may have some slack to dial out of the linkages. Of course all that testing with bridge on TPS so it will not try to dither.

I think we may all measure the closed throttle position slightly differently and that is why I don't bother anymore. Factory trained with factory tools might work but I don't have that option. I tried my best the first time around I did this and got poor results because with the TPS unplugged my engine ran way too fast, maybe 1500 rpm. So I had to close down the t/b's ever so slightly with mechanical linkages in order to get the control range back and also off idle transition right, I think that's about 1000 roughly with TPS unplugged.

The M30 has the exact same issues and I follow the same procedure. Warm engine, unplug TPS, adjust throttle to about 1000 rpm in open loop, adjust and plug back in TPS. On the M30 you are done at that point... easy... maybe check the AFM bypass air.
Post Reply