Afm position

[SilverBullet]

hey all,
Ive had a search through the forum but havent been able to find what im after.
Im thinking bout bolting on a small toyota sc14 from the 1gg, just becaz there cheap and i cant afford turbo right now, and i want a tad more power atm (i want to beat gen3's). I only want a small amount of boost, so whatever it puts out ill stay with.
The 059 ecu should be able to cope with under 6psi right?
Also where should i position afm, before or after the compressor. I was thinking after, but if theres a good reason to put it before then ill try to plumb it in that way. Any suggestions or things i might have overlooked are appreciated.
Cheers
Aaron

[turbodan]

If you go with a RRFPR you can go either way. I had great driveability with a blow through configuration, stock injectors and stock AFM spring tension and a BEGi 2025 RRFPR at about 7 psi. If you place the AFM before the turbo in a draw through layout, it will help conpensate with boost, but it wont really work correctly without a chip mapped for that configuration.

Especially for low boost, you can just use a RRFPR to compensate for the air density. You dont lose any driveability like you would with different injectors and spring tension.

[g00b86]

turbo dan,
If i am reading this post correct, you are saying that at low boost the stock injectors are fine?? This is just news to me so im really shocked that i dont need to buy them. From what i have gathered i was almost sure i needed atleast 24# and was looking into 30# ers to compensate for something low like the 6-7 psi he was looking to do, as am i. I do know, from your many posts and the info here that a begi is a must, hence why i was looking for a cheaper alt. but like you i still think the begi is the way to go. So in his case, if he plumbed theafm after the turbo (ie a blow through) like stock and kept the stock injectors and used a RRFPR all he needs is something to control boost like a manual boost controller and the assorted turbo items like (bov, wastegate, exhaust downpipe, oil lines, mani, etc) and everything should run fine? Im just looking for a little clarification on this b.c if this is true my project will be completed much earlier than i thought. Thanks

[turbodan]

Yes, you can use the stock injectors and chip with a low boost turbo system. The RRFPR takes care of the boost, and everything else works as stock under manifold vacuum.

[g00b86]

Your referring to the TCD chip correct? What else does the chip do besides adjust timing and etc? Is it absolutly needed? I was under the impression, for the longest time, that if i go with 30# inj the begi unit, and the other associated turbo parts that i would have all the bases covered. Now your telling me that i can use stock injectors along with a chip and a begi and i should be fine? Is the chip what will control the boost or do you still need the manual controller?

[philip1]

the BEGI is your RRFPR it increases the fuel flow through your injectors to compensate for the higher density of air in your engine. Boost controll is by way of a wastegate this dumps some exhaust flow before it enters the turbo to controll turbine speed and therefore boost. spending a little extra money for better products will result in a more pleasurable experience.

[turbodan]

The component that controls the amount of boost the turbo produces is the wastegate. Generally speaking, boost controllers only modify the boost signal to the wastegate actuator to increase boost over the amount that the wastegate is set to allow. There are different kinds of boost controllers and different kinds of wastegates.

When I said "stock injectors and chip" I meant the injectors and chip that came in the car from the factory. That would be the stock BMW injectors and the stock BMW chip. That way the car runs great off boost, with the same mileage and emissions as it does NA. Then when the turbo comes on the RRFPR boosts the fuel pressure to handle the extra air the turbo is packing in. Thats all I used for fuel management up to about 9 psi on my 528.

I wouldnt worry about larger injectors until you go to standalone fuel injection. They are not absolutely needed, not until you start pushing past what you can do with the stock injectors and the RRFPR. Thats the only real way to use them efficiently and effectively both on and off boost. A lot of guys install larger injectors and just crank the AFM spring way up tight. That may work, but theres no way it'll make the same mileage, emissions or have the same driveability as a properly tuned system.

[T_C_D]

A lot of guys install larger injectors and just crank the AFM spring way up tight. That may work, but theres no way it'll make the same mileage, emissions or have the same driveability as a properly tuned system.

We have at least 50 customers running this setup and obtaining stock like drivabilty and fuel mpg at cruise. To my knowledge no customer has failed an emissions test.

Todd

[turbodan]

I remember how mine ran around 7-8 psi with 18lbers and a wicked tight AFM. I put the 14.75lb/hr stockers back in. Theres no way it'll will run as good as it does NA with a cranked up AFM and oversized injectors. I didnt say it'd be terrible, but its not going to be just right. Especially with a low boost system, where the RRFPR can take care of it. I wouldnt bother with anything else unless it was necessary.

[T_C_D]

I remember how mine ran around 7-8 psi with 18lbers and a wicked tight AFM.

Dan, I put 30,000 miles on the Buzz Bomb with 30# injectors. It once achieved 31mpg with a 2.93LSD on a trip from CT to OH 2.5 years ago.

My euro 535i with 30# injectors achieved 27mpg on the trip from CT to NC for 5erFest.

It may not have worked on your car but it works on ALL of the TCD kits.

Todd

[turbodan]

I realize that. Driveability is hard to quantify. I'm just saying that all a guy needs for a low boost turbo is a RRFPR on top of the stock injection. That retains the stock tune under manifold vacuum, which is pretty damn good.

There is no way one of your turbo cars drives as well as stock, with the same city and highway mileage and emissions as a NA car with considerably oversized injectors and a cranked up AFM. The level of precision and calibration in the stock AFM is apparent. That goes out the window when you alter the spring tension, especially to that extent. I'm not arguing that it doesnt work pretty well. I realize that you have quite a fleet out there.

I think the question is why you would not recommend a RRFPR on top of stock injection for a low boost system? Pressure locking the injectors?

[T_C_D]

There is no way one of your turbo cars drives as well as stock, with the same city and highway mileage and emissions as a NA car with considerably oversized injectors and a cranked up AFM.

Why not? Please explain it to me? You do realize that Motronic 1.0 and 1.1 both adapt to the larger injectors.

I know it is fact because I have personally experienced it on many cars! Not just my own personal cars but cars we built for customers.

FYI, our m20 turbo kits include a 535i AFM.

Todd

[Boru]

I'll add that with the car running closed loop the ecu can adjust the mixture about +/- 20%. Adjust the AFM to within that tolerance and the Motronic will handle the rest.
My 635 twin turbo (reborn as the TCD race car) has over 40K miles under high boost. I used it as a commuter, 80 miles per day (not highway cruising either). I wouldn't have done that if it had drivability problems. It also passed MA (same as CA) emissions WITHOUT a cat and averaged 27mpg from MA to 5er fest in Boone, NC and back and about 24mpg on my commute.

[Jeremy]

Dan, you also never actually tuned for larger injectors.

You just guessed.

Guesswork is not tuning. A proper tune is essential to getting anything to run properly. Without WBO2 or SOME kind of feedback other than "that feels better than it did before", you're not going to be able to tune it well.

Jeremy

[Jeremy]

I think the question is why you would not recommend a RRFPR on top of stock injection for a low boost system? Pressure locking the injectors?

Because high operating pressures kill Bosch fuel pumps in fairly short order and drivability is excellent with larger injectors, despite what you may think.

Jeremy

[turbodan]

Motronic was designed to adapt to things like air leaks and engine wear. There are, however, certain thresholds for adaptation that set limits for just how much adaptation can take place. Thats why you have to crank the AFM up. And thats where you lose the driveability.

I guess it works well enough, but its not going to be as good as stock. Theres no way. By altering the spring tension, you destroy the factory calibration. You're running the car in a low load portion of the fuel map all the time, until it gets under boost and opens the flap up some more. You know why that doesnt run as well as it does stock.

But seriously, whats wrong with an RRFPR on top of the stock injection for under 10 psi?

[Jeremy]

But seriously, whats wrong with an RRFPR on top of the stock injection for under 10 psi?

RTFP

[turbodan]

Dan, you also never actually tuned for larger injectors.

You just guessed.

Guesswork is not tuning. A proper tune is essential to getting anything to run properly. Without WBO2 or SOME kind of feedback other than "that feels better than it did before", you're not going to be able to tune it well.

Jeremy

I dont know if you saw my last dyno sheet, but I think the AFR's were pretty good for 24lb injectors on a stock chip and M20 AFM. My 13.8 run at the track was on 18lbers and the RRFPR. Thats a pretty good time for a car tuned completely by guessing at things.

I suppose you could still say I just guessed at tuning with motronic though. Now I'm on megasquirt running fuel and spark, with 30lb injectors and no RRFPR. I'd say it runs pretty hard, its definitely faster than it was on motronic, but the fact that it runs at all should be worth some credit. I drive it everyday, and its gotten much better since I worked out some important settings in Megatune. The wideband sensor is in the mail, because I dont really want to go for more than 15 psi without any kind of feedback, and I would like to make sure its running efficiently under low loads. It does seem to be a little thirstier than it used to be, but thats not bad for my just guessing at the tune, just punching in random numbers in the VE tables.

But seriously, whats wrong with an RRFPR on top of the stock injection for under 10 psi?

RTFP

As far as the fuel pumps go, I went for five months and many thousands of miles on the stock fuel pumps. My odo is broken, so I cant say exactly how many miles, but I'd bet well over 10k. Unless that kind of operation slowly wears on them and kills them all at once, I dont see it. I'm still on those pumps. If they're damaged, I sure haven't noticed it yet.

You should note that you got that post in while I was typing the reply you quoted. No need for this angry stuff.

[SilverBullet]

Wow! I did not expect this....
Anywho, just so we dont forget its a supercharger not turbo im talking bout, but no real difference other then when boost comes on.
So with the m30b35 and 059 motronic i should be right for like 6 or 7psi with just RRFPR. And do u think ill need to run a BOV? Should this be put before or after Afm?
Cheers for all the help
Aaron

[Jeremy]

I dont know if you saw my last dyno sheet, but I think the AFR's were pretty good for 24lb injectors on a stock chip and M20 AFM. My 13.8 run at the track was on 18lbers and the RRFPR. Thats a pretty good time for a car tuned completely by guessing at things.

What you've been able to do without a WBO2 is just short of miraculous. Realize though that WOT tuning is just part of the equation, as I'm sure you're realizing now with the megasquirt. Part throttle tuning can be a bit of a pain.

But seriously, whats wrong with an RRFPR on top of the stock injection for under 10 psi?

RTFP

As far as the fuel pumps go, I went for five months and many thousands of miles on the stock fuel pumps. My odo is broken, so I cant say exactly how many miles, but I'd bet well over 10k. Unless that kind of operation slowly wears on them and kills them all at once, I dont see it. I'm still on those pumps. If they're damaged, I sure haven't noticed it yet.

More than a few people have had issues with the Bosch pump running at high operating pressures. Eventually it just can't make the same peak pressure anymore. Todd has seen it a few times, which is why he uses the high capacity in tank pump.

You should note that you got that post in while I was typing the reply you quoted. No need for this angry stuff.

Dude, there's an hour and 4 minutes between my post and your reply, you just plain missed it. 8) I probably should've put it all in one post, but the second part occured to me after the fact.

Jeremy

[russc]

The same AFM was used on many Porsches that made 100hp more than the M30! This was with just spring tension changes. There is so little "drivability" degredation from this change itls not worth worrying about.

RussC

[turbodan]

I dont know if you saw my last dyno sheet, but I think the AFR's were pretty good for 24lb injectors on a stock chip and M20 AFM. My 13.8 run at the track was on 18lbers and the RRFPR. Thats a pretty good time for a car tuned completely by guessing at things.

What you've been able to do without a WBO2 is just short of miraculous. Realize though that WOT tuning is just part of the equation, as I'm sure you're realizing now with the megasquirt. Part throttle tuning can be a bit of a pain.

Part throttle tuning has been most of the work even with Motronic. I drive this car every day, and it does me no good if it only runs at full throttle under boost. I've been there, done that too. I dont have a wideband 02 on my kawasaki either, but I manage to tune that. Its not impossible.

But seriously, whats wrong with an RRFPR on top of the stock injection for under 10 psi?

RTFP

As far as the fuel pumps go, I went for five months and many thousands of miles on the stock fuel pumps. My odo is broken, so I cant say exactly how many miles, but I'd bet well over 10k. Unless that kind of operation slowly wears on them and kills them all at once, I dont see it. I'm still on those pumps. If they're damaged, I sure haven't noticed it yet.

More than a few people have had issues with the Bosch pump running at high operating pressures. Eventually it just can't make the same peak pressure anymore. Todd has seen it a few times, which is why he uses the high capacity in tank pump.

Alright. I havent. Maybe thats the nature of stock fuel pumps wth 200k miles on them. I guess I'll take your word for it.

You should note that you got that post in while I was typing the reply you quoted. No need for this angry stuff.

Dude, there's an hour and 4 minutes between my post and your reply, you just plain missed it. 8) I probably should've put it all in one post, but the second part occured to me after the fact.

Jeremy

I had typed a reply to TCD's post at 8:36 and accidentally wiped it out with a clumsy tap on the laptop. So I had to dooeet all over again. I was also watching TV while posting. Sweeney posted one reply, and you got two in before I posted that message. Shitting you I am not.

The same AFM was used on many Porsches that made 100hp more than the M30! This was with just spring tension changes. There is so little "drivability" degredation from this change itls not worth worrying about.

RussC

It was the same size AFM, thats about it. The differences would be the potentiometer in the AFM, the inner curve of the AFM and the mapping in the ecu. It can be made to work well, but without remapping its never going to be just right. If you dont believe me, bolt one of the Porsche AFM's on your 535. See how it runs. Its a completely different part. Just like the small frame AFM's on Ford's mid 80's 2.3l turbo engines was completely different than a regular BMW M20 AFM.

Wow! I did not expect this....
Anywho, just so we dont forget its a supercharger not turbo im talking bout, but no real difference other then when boost comes on.
So with the m30b35 and 059 motronic i should be right for like 6 or 7psi with just RRFPR. And do u think ill need to run a BOV? Should this be put before or after Afm?
Cheers for all the help
Aaron

That is correct. IN MY OPINION, you will be fine running just a RRFPR at 6-7 psi. You will need a bypass/blow off valve with either a turbo or a supercharger. You will need a much bigger blowoff valve for a supercharger, as it makes boost by engine speed and not engine load. So when you throttle back at 6000 RPM, it keeps trying to pack in air as if you were still at full throttle until the engine speed decreases. A supercharger blowoff valve will be open pretty much all the time, except for when youre really on the throttle.

You'll want to place the blow off valve in the charge pipes BEFORE the AFM. If you install it after the AFM you will be blowing off metered air, which is very bad. Its like a reverse air leak, it will run super rich if you blow off metered air. Bad times.

[Mike-TurboE24]

You'll want to place the blow off valve in the charge pipes BEFORE the AFM. If you install it after the AFM you will be blowing off metered air, which is very bad. Its like a reverse air leak, it will run super rich if you blow off metered air. Bad times.

I think there is confusion here. The BOV goes on a charge pipe after the compressor and before the manifold. The BOV should discharge into an intake pipe after the AFM and before the compressor (or vent to open air.)

[turbodan]

You'll want to place the blow off valve in the charge pipes BEFORE the AFM. If you install it after the AFM you will be blowing off metered air, which is very bad. Its like a reverse air leak, it will run super rich if you blow off metered air. Bad times.

I think there is confusion here. The BOV goes on a charge pipe after the compressor and before the manifold. The BOV should discharge into an intake pipe after the AFM and before the compressor (or vent to open air.)

Recirculating the bypassed boost back into the metered air supply would only be necessary if you place the AFM before the compressor. I'm describing a blow-through system. A draw through system, with the AFM metering the compressor inlet, would be different. I'd say a draw-through would be impossible with a supercharger due to the amount of air that would be bypassed during part throttle operation.

Specifically, the BOV can be anywhere between the compressor and the throttle plate. The best place is on the hot side charge piping, after the compressor but before the intercooler. If you're using a draw through system with the compressor blowing metered air, you would need to recirculate the extra boost to the compressor inlet on the metered side of the AFM.

I like the blow through system because it makes any small leak in the charge pipes completely harmless, and theres no need to plumb the bypass valve back into the charge pipes. Now I'm using MAP based fueling, so it doesnt even matter. As long as the pressure gets through to the manifold its all good.