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MS with ITBs
coyoteboy - 19/11/11 at 12:46 AM

I'm looking at running ITBs on my V8 with a squirt to run it, question is has anyone done similar here? I've squirted several vehicles now and those with ITBs have given such an unstable MAP (and high, 85kpa at idle) that it effectively gave no resolution for tuning and would require alpha-n which I'm not keen on.

Any experience of ITBs on V8s and megasquirt?

atm92484 - 19/11/11 at 02:21 AM

MS3 has an ITB mode that automatically blends MAP tuning at low load and alpha-n for high load. Might be worth investigating.

matt_gsxr - 19/11/11 at 09:10 AM

Later versions of MS (based on MS2 chip) do a better job of sampling the MAP. If you do the tricks with fuel filter and decent length of hose (mechanical signal filtering) and use the later MS2 chip then I think you should be able to get a decent idle using speed-density (i.e. MAP based). This worked for me (ITB's on a 4cylinder).

Have you tried ITB mode yet?

The alternative would be to use MAF like most of the OEM's do, but it would be more bother.

ChrisW - 19/11/11 at 11:28 AM

How do you use MAF on ITBs?? If you're then restricting them by using an air box and drawing the through a MAF surely it defeats the object of going ITB in the first place?

Chris

MikeRJ - 19/11/11 at 11:41 AM

quote:
Originally posted by ChrisW
How do you use MAF on ITBs?? If you're then restricting them by using an air box and drawing the through a MAF surely it defeats the object of going ITB in the first place?

Chris


As long as the MAF is sized accordingly it shouldn't present much in the way of restriction. However, ITBs are usualy used in conjunction with longer duration cams and MAF sensors don't like these at all.

coyoteboy - 19/11/11 at 12:10 PM

Ive not used ITB mode in tuning as the engines I've tuned with ITBs have more or less worked out (enough to deal with and do what they do). I've used fairly massive hose lengths which does tend to help reduce the spikey signal, not yet stuck a fuel filter inline but still don't see it pulling a "normal" vacuum but they were bike engines and I'm not sure if the cam setups on them is more likely to lead to higher idle MAPs. I want this one to be road drivable and have decent reliability. I'd considered boxing the ITBs into an airbox which could have a flow meter on it, but it'd be huge and I was trying to avoid it at all costs really. I think that the MS2 code does the table switching jiggery pokery between alpha-n and SD too, MS3 has some nice additional features but at 2x the cost of the MS2 it's up into normal aftermarket ECU terrritory and I'd rather just buy a supported solution if I were going to spend that much - this is where I think the MS folk have shot themselves in the foot.

I'll have a go with one of my usual engines and a fuel filter, see if I can get more usable results. I scoped actual port pressure at one port the other day and didn't see any pressure lower than about 70kpa during the cycle, so I don't think I'm ever going to get the table resolution I need - ITBs are a bit of a difficult one for me!

matt_gsxr - 19/11/11 at 02:10 PM

I think that BMW M3 and M5 ( E30 and E28) used ITB and a MAF. Free flowing MAF (hot wire type) on the inlet of a big airbox would be the method. But I can understand you not having space. Anyway, not sure its a great idea anyway.


Back to the OP.
I think the big long tube solution is the same as a restriction and fuel filter (it just provides additional damping).

I don't think MS3 offers anything over MS2 for your particular problem. Both can handle ITB mode, which is aimed squarely at your problem.

I agree with you. MS3 doesn't make that much sense to me either, actually I am a bit surprised that the prices don't come down with time and numbers produced, but they don't seem to. I assume it is simply because that there are several small suppliers whereas the cheap way of doing this would be to mass-produce somewhere with dirt cheap labour.

Matt

coozer - 19/11/11 at 02:41 PM

I'm going to do the same and chuck the MAF and use the TPS.

BaileyPerformance - 19/11/11 at 10:05 PM

quote:
Originally posted by coyoteboy
I'm looking at running ITBs on my V8 with a squirt to run it, question is has anyone done similar here? I've squirted several vehicles now and those with ITBs have given such an unstable MAP (and high, 85kpa at idle) that it effectively gave no resolution for tuning and would require alpha-n which I'm not keen on.

Any experience of ITBs on V8s and megasquirt?


Just wandering why you don't like alpha N? No chance of using MAP on throttle bodies. If you can make some sort of common inlet plenum to sit on top of all 8 throttle you can use a MAF.
MAF is the best way to go on any engine, i have done a couple of TR6s and used a MAF - i found this to give the best drivablity. Also did a 5.5L TVR using an F150 pickup truck MAF (90mm), fuelling was spot on, all using MS2.

Let me know if you need any info/help.

Good look with your project!

coyoteboy - 21/11/11 at 10:58 AM

quote:

Just wandering why you don't like alpha N? No chance of using MAP on throttle bodies. If you can make some sort of common inlet plenum to sit on top of all 8 throttle you can use a MAF. MAF is the best way to go on any engine, i have done a couple of TR6s and used a MAF - i found this to give the best drivablity. Also did a 5.5L TVR using an F150 pickup truck MAF (90mm), fuelling was spot on, all using MS2. Let me know if you need any info/help. Good look with your project!


Cheers, couldnt use alpha N as it was a track-only vehicle which didn't have a TPS installed (it did, but it was damaged and there was no chance of getting a replacement in time for the event). I've actually now just got time to replace it and will try again with alpha-n to see how I get on. I'd love to do MAF for ease of tuning but I think I'll lose the aesthetics and sound if I surround it with a carbon pouch, too, which is part of the fun of this build. I may have to eventually I guess!

coyoteboy - 21/11/11 at 11:05 AM

quote:

I agree with you. MS3 doesn't make that much sense to me either, actually I am a bit surprised that the prices don't come down with time and numbers produced, but they don't seem to. I assume it is simply because that there are several small suppliers whereas the cheap way of doing this would be to mass-produce somewhere with dirt cheap labour.


Especially considering it's only based on a slightly different processor and a couple of extra, small, pcbs and still uses the original mainboard (a bit of a gripe of mine). If they'd revamped the whole board and developed better interconnects I could understand it but it currently looks like it's using the same mainboard with another daughter card (made on teh cheap too, looking at the PCB material) and all for the price of a pro item.