NA is best - 3.1L M20 w/ ITB's

[Raxe]

In general big cam with overlap has more contamination of exhaust into intake due to reversion at low load and rpm so it burns alot slower therefore you need to light the fire a little earlier. of course this assumes the setup is correct and if you ask for X* you are actually getting X*. If the thing is offset then..........

The other thing is if the throttle isn’t sync'd then a couple cylinders could be running too lean and this slows the burn down so it happens very late and can even continue into the exhaust. if you get lean enough it will still be burning by the time the inlet valve opens and you can get backfires and popping in the inlet.

You should invest in a sync tool they are so easy to use rather than screwing around with pressure tapping’s etc that require tiny restrictors to dampen all the pulses and it tells you actual airflow instead of vacuum



yeah the problem with ITB is the fuel curve is very steep at low throttle position so you need more load point down there.

also this thread is back alive, Fporro has a map that might interest you there

http://www.e30tech.com/forum/showthr...=33028&page=12

Man, thanks again for the advice. You're really helping me along here and I appreciate it. I have an STE synchrometer lined up for the weekend to hopefully get them dialed in as close as possible now as per Ramas guide and I'm thinking I'll aim for 900rpm as an idle.

Hadn't even realized e30tech is back, I was just browsing the archived pages until now... Franks map and info looks like it's going to help me tremendously! Very excited. :D

Will report back with results when I get the new numbers entered.


A picture for anyone just looking at pics:

[Phoenix]

Yeah that first picture was set up very very wrong, I've spent the last two afternoons fixing it little by little as I figured out what needed correcting.

- Switched the pins on the TPS connector (whoops) and I'm actually getting a decent ADC range now.
- Changed to alpha-n and disabled all of the MAP input.
- Changed the ignition timing to a proper table and redid all of the table scaling for alpha-n.
- Actually wired my wideband to the MS and set it to read from there vs the narrowband O2.
- Mechanically synchronized the throttles a bit better with a feeler gauge and set a reasonable idle but I still need to do a proper vacuum sync now that it runs.

I've been playing around with the VE and AFR tables and managed to get a decent idle mixture of 13.5-14.5 at 1100rpm, I'm still having a hell of a time with anything under load but it's baby steps... I'm pretty much starting from scratch with no experience and learning along the way.

Is this looking better?



I don't think the scaling is off? Otherwise I'm really not sure what to do about the pulsewidth.

I know that Bosch rates their injectors at a fuel pressure of 43.5 psi, or 3 Bar. What is your pressure at the rail? The higher the pressure, the more they will flow.

[Raxe]

I know that Bosch rates their injectors at a fuel pressure of 43.5 psi, or 3 Bar. What is your pressure at the rail? The higher the pressure, the more they will flow.

It's the stock 3 Bar FPR, I haven't actually measured the pressure but I'm assuming it's working properly...

I've considered the effect that the lower intake vacuum may have on how the regulator works at low load, perhaps that's contributing to a rich idle but I have no idea how you'd tune that out besides just getting the vacuum as strong as possible and adjusting the fuel table as necessary.

[ForcedFirebird]

Do you have the regulator to a vacuum manifold, or a single cylinder?

[Raxe]

Do you have the regulator to a vacuum manifold, or a single cylinder?

I have it hooked up to a single cylinder with no splices. Ditched the original vacuum block idea in favor of simplicity.

[ForcedFirebird]

Might not be a good idea, though. With it hooked up to one cyl, it will pulse vacuum every time that cylinder pumps. It's interesting to watch a mechanical vacuum gauge hooked to just one. I have been leaving the FPR open on open trumpet cars and using a manifold when they have them.

[jeenyus]

if you're that concerned though, why not just go with a electronic FPR that's manageable through MS?

[nando]

Even if it's electric it still needs to be referenced to intake pressure somehow in order for the injectors to behave in a linear fashion. I don't think I've ever heard of such a thing on an M20.

Also, going electric seems like a lot of hassle - I think a vac distribution line would be a better effort, and maybe that's why you couldn't get the "Blended" Alpha-N/SD mode to work. The blended mode should actually be easier to tune, since it factors relative pressure into the equation and not just your TPS, which isn't necessarily linked 100% to engine load. But it's not going to work very well with just one referenced cylinder for MAP.

FYI lower vacuum makes no difference to the effectiveness of a FPR. It just needs to provide a constant 3 bars of ambient pressure relative to manifold pressure - so if the intake vacuum is lower, the FPR automatically compensates by increasing pressure to stay at a 3 bar equilibrium. But by tying it to just one cylinder, you'll get pressure spikes every time the valve opens and closes on that cylinder..

[CorvallisBMW]

Damn, not sure how I missed this thread, but sub'd!

[Raxe]

Might not be a good idea, though. With it hooked up to one cyl, it will pulse vacuum every time that cylinder pumps. It's interesting to watch a mechanical vacuum gauge hooked to just one. I have been leaving the FPR open on open trumpet cars and using a manifold when they have them.

Oh that's an interesting point, I hadn't considered the pulsing effect. Probably was messing up the MAP reading too as nando suggested since that line was set up the same way.

So until I set up a vacuum manifold it would be better to temporarily leave the line off the FPR for a more stable pressure? And if so, expect to compensate for a richer idle mixture for now because the regulator is seeing no vacuum and running at full load?

[ForcedFirebird]

Correct. Leave it to atmosphere and tune it out, or use a vacuum manifold to average the cylinder pressures. Even a manifold won't be very accurate without a buffer/canister, the pulses will still be strong.

[nando]

you can use a large lawn mower fuel filter as a buffer/canister, cheap and effective.

[Northern]

I've always thought about either the shop air manifolds - some come with enough ports.

Or something for an aquarium like this:

http://www.ebay.co.uk/itm/6-x-4mm-x-8mm-Barbed-Air-line-Manifold-Air-Stone-Pump-Pond-Aquarium-Airline-/282237183461

Ideally, CAD something up and 3d print it as one piece...

[digger]

rama sells one of those with the kit, does FPR, booster, ICV etc. if you still dont like the FPR with ref in the vacuum rail because it still pulses too much for your liking just open it to atmosphere and route the open ended hose somewhere that wouldn't shoot fuel onto the exhaust if the FPR ruptured. the other option is a restrictor in the vacuum line that is a great way to dampen pulses on steady state but may react slower

[ForcedFirebird]

I've always thought about either the shop air manifolds - some come with enough ports.

Or something for an aquarium like this:

http://www.ebay.co.uk/itm/6-x-4mm-x-8mm-Barbed-Air-line-Manifold-Air-Stone-Pump-Pond-Aquarium-Airline-/282237183461

Ideally, CAD something up and 3d print it as one piece...

I found plain old fuel rail stock works well. Drill/tap the flat for threaded fittings, then the two ends can be used for the IAC and brake booster. The latest RHD stuff comes with a small manifold now.