Balancing S38 ITBs

[macsm5]

Dean, love the sticker. I'm a little way away from being ready to undertake this. Critical to the balancing procedure is correctly adjusted valves, which is a bit of a black art since most of us are going somewhere between .012 and .014 depending on which shims give the closest gap to spec. I suppose that's one of the things that balancing addresses. In addition, setting up the butterflies and linkage mechanism is another important step before attempting to balance the bypass ports. Any plans to add this equipment to the kit/instructions? I can host a .pdf file for you if you want to include it in the thread.

Finally, I would recommend ordering parts number 14 (o-rings) and 16 (blue caps) ahead of time. Compromised o-rings can invalidate the adjustments.

Hi Dean,

In your instructions re: mechanically synchronizing the throttles, you mention to replace the o-ring in the main idle adjuster, in the RealOEM diagram AHAB posted is the main idle adjuster part number 33 and the main idle adjuster "o" ring to replace number 34?

Thanks!

[macsm5]

Dean, love the sticker. I'm a little way away from being ready to undertake this. Critical to the balancing procedure is correctly adjusted valves, which is a bit of a black art since most of us are going somewhere between .012 and .014 depending on which shims give the closest gap to spec. I suppose that's one of the things that balancing addresses. In addition, setting up the butterflies and linkage mechanism is another important step before attempting to balance the bypass ports. Any plans to add this equipment to the kit/instructions? I can host a .pdf file for you if you want to include it in the thread.

Finally, I would recommend ordering parts number 14 (o-rings) and 16 (blue caps) ahead of time. Compromised o-rings can invalidate the adjustments.

Hi Dean,

In your instructions re: mechanically synchronizing the throttles, you mention to replace the o-ring in the main idle adjuster, in the RealOEM diagram AHAB posted is the main idle adjuster part number 33 and the main idle adjuster "o" ring to replace number 34?

Thanks!

[HealeyBN7]

Michael,

Yes. That is correct. The main idle adjustment is the big screw or part number 33 and the o-ring is 34 (11631271346). For some reason, BMW Real OEM didn't list the size of this o-ring as they have for others, but you may be able to match it if you have access to an assortment.

Good luck and let us know how it goes!

Dean

[HealeyBN7]

Mantis whereabouts...

Currently it is on loan to Michael (macsm5) - NoCal - Expected return May 4-5.

Brad (bdalessio) is next on the list - NoCal

Then Eric (ronin) - Spartanburg, South Carolina

Once it is back in SoCal after Eric, perhaps we can schedule in the local sessions.

Sound fair?

Let me know if I missed anyone.

Dean

[HealeyBN7]

Well....I wasn't planning on making another Mantis, but this copy is going to Brad. Thank you Brad!



It has a few improvements:

This version uses nylon barbs on a larger 7 vs 6 port manifold. The larger manifold eliminates 90 degree fittings. The nylon barbs provide a better seal to the vinyl tubing and eliminate the wire ties. I also added thicker (by 1mm OD) high temperature silicone hose to the ends of the vacuum tubes. I think this is a necessary improvement to ensure the business end doesn't deform from heat.

There is also a machined aluminum barb fitting on the large hose. I had to make this one in the lathe as I could not find a 3/16 to 3/8 reducer barb.





It was a good exercise to see how much it cost to make and how much time it takes - too much of both.

Brad should get his Mantis by the end of the week. Eric - I guess you will be next in for the rental as soon as Michael and Brad are finished.

Dean

[ronin]

If you are talking to me, Eric, then just let me know. If you meant a different Eric, that is ok, just let me know where I fit in the schedule. The new and improved version sounds nice. Looking forward to it.

Take care,

Eric

[HealeyBN7]

FYI - The Manometer Kit It is on the road again for a quick loan to David as MinneapM635 in Minneapolis. Should be back and available in a couple weeks.

By the way, shipping seems to have gone up to $20 with insurance. sorry.

Dean

[Das_Prachtstrasse]

What an incredibly fantastic thread. This information is invaluable and will prove to be a cornerstone of mine once this ITB'd M30 is off the ground. Dean, I would be very much appreciative if you would allow me to replicate your design for my own uses as despite my eagerness, international shipping on a borrowed part is folly. Failing that, if you could perhaps be swayed into manufacturing another that would be even more excellent as I'll be needing this tool in due time, and it would be highly useful to those local S38 owners in the click. You'd have to be sure to install the ruler upside down, though.

[HealeyBN7]

I may have a wait until I retire to make another one, but in the mean time feel free to knock off a copy for you and your friends down under. I am thinking that you should be able to figure out all the bits by looking at the pictures. If you need something special let me know. When I put together the second kit for Brad I was shocked how quickly the parts totaled to more then a couple hundred dollars. You of course could save some money of you reused your personal fuel pressure gauge and dial indicator, but be aware that buying the fittings in small quantities is just not frugal.

It is a fun weekend project - get to it!

Dean

[MinneapM635]

Got the Mantis on Monday and immediately plugged it in to get a baseline of where I was at. Last time I synched the throttles was probably 2013 and I used a single mechanical gauge and with all the pulsing, and pinching of the lines, it probably wasn't the best. Here's a video of the readings without any adjustment. Warning, I am a novice at taking and posting videos online... AND keeping my garage tidy.

https://youtu.be/KXkaAa2kSFo

A few quick adjustments and the result:

https://youtu.be/hnNzKgXWEpI

This was without any of the prerequisite "remove the screws, replace o-rings, bottom out and turn out 1 turn" baseline adjustment. So, I set off to do just that last night and wouldn't you know, the o-ring on the idle speed adjustment screw basically disintegrated upon removal of the screw. So, replacement rings ordered on fast shipment. I hope to have the Mantis back in the mail by Monday/Tuesday next week.

Dean, I give credit to you for the tool in the description of the videos. Let me know if you would like me to remove or add any other information. Want to make sure you get the appropriate credit for this great tool.

Thanks,
Dave

[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]

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]

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]

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]

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]

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

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]

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

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]

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]

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]

That makes sense, thank you for clarifying.

[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]

Wow. That sounds smoother too!

[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]

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]

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]

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]

Would a motorcycle synchronizing tool like the http://www.motionpro.com/product/08-0411 do a similar job as the MantisManometer?

[HealeyBN7]

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]

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]

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.