Blowoff valve placement, is this ok?

[demetk]

Just wondering if this is as good a location as any for the blow-off valve? How do you go about adjusting it?

One other question regarding the O2 tap. I'm using a N.O. Hobbs pressure switch shown just below the blow-off valve. Is a 1 psi set point too low or high to trigger the O2 cutoff circuit?

TIA

[George]

Placement of BOV is fine.

Not sure about the switch. Some M1.3 guys can chime in.

[Martin in BellevueWA]

If you have to use a stock AFM, it prolly would be better to place it in front of the turbo. Clock the thing about 20 notches tighter too; mark the stock setting.

[demetk]

If you have to use a stock AFM, it prolly would be better to place it in front of the turbo. Clock the thing about 20 notches tighter too; mark the stock setting.

You're talking about the spring tension? Why 20?

[cvillebimmer]

If you have to use a stock AFM, it prolly would be better to place it in front of the turbo. Clock the thing about 20 notches tighter too; mark the stock setting.

You're talking about the spring tension? Why 20?

20 is about how much I had to tighten the spring with 24lb injectors to get the mix right under part throttle boost.

If you leave it the factory setting, it will be way to rich under part throttle boost.

[demetk]

If you have to use a stock AFM, it prolly would be better to place it in front of the turbo. Clock the thing about 20 notches tighter too; mark the stock setting.

You're talking about the spring tension? Why 20?

20 is about how much I had to tighten the spring with 24lb injectors to get the mix right under part throttle boost.

If you leave it the factory setting, it will be way to rich under part throttle boost.

Ok thanks, I'll monitor the fuel mix. To be clear I'm still using the stock Motronic 1.3 system on this B35.

[cvillebimmer]

What size are your injectors?

1.3 motronic can adapt to 24lb injectors without any adjustment to the AFM under all vacuum conditions (idle, cruise and non-boost acceleration). However, when the O2 clamp kicks in, especially on part throttle boost, the mixture will be way too rich. In my case, I saw low 8s before adjusting the AFM. IIRC, I'm at 16 clicks now.

I still see AFRs lower than I'd like at the onset of boost at low RPM (high 9s/ low 10s) and slightly higher than I'd like getting up towards 6k RPM (high 13s). This it the main reason I'm switching to MS. You will likely see different results with your car. I have no way of knowing how much impact Paul Burke's work has on my engine's breathing capabilities.

[demetk]

What size are your injectors?

1.3 motronic can adapt to 24lb injectors without any adjustment to the AFM under all vacuum conditions (idle, cruise and non-boost acceleration). However, when the O2 clamp kicks in, especially on part throttle boost, the mixture will be way too rich. In my case, I saw low 8s before adjusting the AFM. IIRC, I'm at 16 clicks now.

I still see AFRs lower than I'd like at the onset of boost at low RPM (high 9s/ low 10s) and slightly higher than I'd like getting up towards 6k RPM (high 13s). This it the main reason I'm switching to MS. You will likely see different results with your car. I have no way of knowing how much impact Paul Burke's work has on my engine's breathing capabilities.

I'm running stock 19lb injectors. I haven't able to do any tuning because I hadn't built my O2 clamp yet, and without it, the engine was leaning out even under very slight boost. I'm keeping my foot of it for now.

Now that I have the O2 clamp in place I can start the tuning. The 19lb injectors should be good for 6psi, no? Otherwise I'll get some 24lb injectors.

BTW, at what psi does your O2 clamp work at? I've bench set my Hobbs pressure switch to click at 1psi.

Thanks.

[cvillebimmer]

What size are your injectors?

1.3 motronic can adapt to 24lb injectors without any adjustment to the AFM under all vacuum conditions (idle, cruise and non-boost acceleration). However, when the O2 clamp kicks in, especially on part throttle boost, the mixture will be way too rich. In my case, I saw low 8s before adjusting the AFM. IIRC, I'm at 16 clicks now.

I still see AFRs lower than I'd like at the onset of boost at low RPM (high 9s/ low 10s) and slightly higher than I'd like getting up towards 6k RPM (high 13s). This it the main reason I'm switching to MS. You will likely see different results with your car. I have no way of knowing how much impact Paul Burke's work has on my engine's breathing capabilities.

I'm running stock 19lb injectors. I haven't able to do any tuning because I hadn't built my O2 clamp yet, and without it, the engine was leaning out even under very slight boost. I'm keeping my foot of it for now.

Now that I have the O2 clamp in place I can start the tuning. The 19lb injectors should be good for 6psi, no? Otherwise I'll get some 24lb injectors.

BTW, at what psi does your O2 clamp work at? I've bench set my Hobbs pressure switch to click at 1psi.

Thanks.

At 9psi, I think I'm nearing the limits of the 24lb injectors.

I think the clamp kicks in below 1psi, but it's hard to tell for sure. Below is a pic of my clamp. I can't find specs on it, but perhaps you'll have better luck.

[Jays535is]

^
^
^
I have that same switch if anyone needs it, I'm running a Miller/Warchip so no longer need it.

[demetk]

Thanks,

Yeah, I had two of those switches and both had ruptured diaphragms when tested. So I'm going with a Hobbs switch instead.

Since I wanted my a/r gauge to still work and also have an LED indicator to tell me that the O2 clamp was working, I used a DPDT relay.

Gauges from left to right. oil pressure, boost, wideband, a/r (I need to add the LED beside the a/r gauge).



Here's a schematic of the circuit I built.

[George]

One more reason to go to MS.

[demetk]

One more reason to go to MS.

Yup, I went backwards from MS I to Motronic 1.3, replaced the engine, added an M5 clutch, added the turbo, and after countless hours fixing tons of problems, I finally added a 10 year old universal cat and got the car to pass emissions on the first try with no warmup. I was mildly surprised.

If I don't blow up the engine in the interim, more work is being planned on it but it will need to wait after my kitchen is done.

Thanks for the answers so far guys. I really appreciate the responses here.

[demetk]

So I took a trip to the drug store today and briefly tested the O2 clamp. The thing works, mixture went rich and the "check engine" light went ON, I presume because it lost the O2 sensor.

So what resistor do you need to add to the ECU's O2 reference signal of .5 volts to simulate a .2 volts signal? Can you just ground the reference signal or will the ECU still think it lost the O2 sensor?

[Jeremy]

Welcome to the sorta-wonderful world of a boosted motor running M1.3. If the ECU sees an O2 signal, it will try to correct for it, so sending it a fake signal is generally not done. You'll need to clear the ECU periodically to keep it running correctly without some sort of solution though. The more errors it throws, the more wonky the tune will get. The signal conditioning you're contemplating might work in conjunction with the O2 clamp, but most people I've talked to go to standalone of some kind as opposed to trying to work around the limitations of Motronic. It's less "kludgey" in the end, and thus more reliable, predictable, and easier to troubleshoot.

[demetk]

Thanks. If 1.3 becomes a mixed bag under boost then I will be reconsidering standalone. First I'm going to check if conditioning the O2 signal will work under the O2 clamp. Secondly, I'm going to pull the check light.

[cvillebimmer]

Thanks. If 1.3 becomes a mixed bag under boost then I will be reconsidering standalone. First I'm going to check if conditioning the O2 signal will work under the O2 clamp. Secondly, I'm going to pull the check light.

I actually like the check engine light. It's sort of a visual reminder that the clamp is working and the mixture is enriched. It only comes on under boost and turns off a few seconds after returning to N/A conditions.

[George]

The stock M30 (b34/b35) injectors flow just a tad over 21lb/hr. Check the factory manual if you don't believe me.

[Jeremy]

The stock M30 (b34/b35) injectors flow just a tad over 21lb/hr. Check the factory manual if you don't believe me.

At what fuel pressure? I seem to remember BMW using a higher pressure spec than "standard" for their fuel injector ratings.

Jeremy

[George]

The stock M30 (b34/b35) injectors flow just a tad over 21lb/hr. Check the factory manual if you don't believe me.

At what fuel pressure? I seem to remember BMW using a higher pressure spec than "standard" for their fuel injector ratings.

Jeremy

3bar. The actual flow is given in cc/min. A simple conversion to lb/hr

[brody]

It's funny to see the "trickery" suggestions in this thread. Why not just get a PROPER tune for the Motronic so that all other mechanical/electric parts are functioning as they are supposed to, or convert to stand-alone?

To say Motronic will adapt to 24# injectors is hogwash, sure the car will run, but the O2 sensor will be pegged and it is not intended to operate like that.

Turning the AFM clicks every which way is also going to cause performance loss. You are losing resolution when you do this.

Sure you will be able to boost your car, sure it will make more power than stock when you do all this trickery, but you will be missing out on pristine driveability and power. Why use an octagon for a wheel when you can use a circle?

As mentioned, if you put the AFM in front of the turbo, you will have better results at any + PSI, the AFM will just blow wide open when on the pressure side. If you do run it Preturbo, you will need to recirculate the pressure in front of the turbo but behind the MAF. If you don't, it will spike rich when it vents to atmosphere.

M1.3 is great when it comes to boost if you have tuned it PROPERLY. You don't see any reputable tuners tuning a car in these manners EVER because it just doesn't work when you compare it to something done the right way.

FWIW, if budget is a problem, think of a few hundred more dollars to alleviate headaches and constant dicking as well as the most efficient means of power delivery.

[demetk]

It's funny to see the "trickery" suggestions in this thread. Why not just get a PROPER tune for the Motronic so that all other mechanical/electric parts are functioning as they are supposed to, or convert to stand-alone?

To say Motronic will adapt to 24# injectors is hogwash, sure the car will run, but the O2 sensor will be pegged and it is not intended to operate like that.

Turning the AFM clicks every which way is also going to cause performance loss. You are losing resolution when you do this.

Sure you will be able to boost your car, sure it will make more power than stock when you do all this trickery, but you will be missing out on pristine driveability and power. Why use an octagon for a wheel when you can use a circle?

As mentioned, if you put the AFM in front of the turbo, you will have better results at any + PSI, the AFM will just blow wide open when on the pressure side. If you do run it Preturbo, you will need to recirculate the pressure in front of the turbo but behind the MAF. If you don't, it will spike rich when it vents to atmosphere.

M1.3 is great when it comes to boost if you have tuned it PROPERLY. You don't see any reputable tuners tuning a car in these manners EVER because it just doesn't work when you compare it to something done the right way.

FWIW, if budget is a problem, think of a few hundred more dollars to alleviate headaches and constant dicking as well as the most efficient means of power delivery.

Please don't get the wrong impression here and, FWIW, budget is definitely not a problem. This car has been 100% DIY all the way and it's going to stay that way. The only thing I'm going to farm out will be paint because I'm not equipped for the entire car. I am doing everything else with the car, that's what a hobby is all about. I have plenty of knowledge built up from having multiple bimmers over the last 20 years, including my 745 which I always tuned myself and drove for 10 years and to 300k miles.

Blow through vs pull through AFMs? There are opinions on both sides. I weighed the opinions and chose the blow through approach.

Heard about the O2 clamp here and thought it was a plausible approach.

AFM adjustments? I know all about them. I even have my own write-up on it. I mixed and matched components from various AFMs and built my own 745 AFM. I like re-purposing things.

This project has been and will always be about the learning experience. There are some folks here who can run rings around me when it comes to design & build, and that's ok, because it's good to have role models.

cheers.