Very big bore throttle body?

[eta]

I have found it give better fuel economy even on this old machine.

[phelix]

IAt the moment I run a BBTB, a ported inlet manifold and Miller MAF conversion. I dynoed before and after. After the MAF conversion, BBTB and ported inlet manifold, things are smoother and with more power from earlier on the results are interesting: between about 4300-5800rpm there are instances where power is greater by as much as 7-8 Kw with a lower figure of 2-3 kw or so. Around 4-5 Kw seems to be the median. This would explain, along with the increase in torque (though not as much as described by Miller) why the car really seems to start to boogie beyond 4000rpm. If anything, running on the standard Miller map is compromised by the BBTB and inlet manifold. Put the car on a rolling road and tune and results would have been better.

Not wishing to come across as p*ssing in your chips but the MAF conversion comes with a new chip - I wonder how much of the power increase is attributable to the chip vs the MAF/BBTB?

[AlpineAde]

Fair question, mate.

To answer: I have no idea.

The chip itself is primarily a unit designed to allow the MAF to function properly.

After speaking with Brody from Miller and discussing the graphs he feels that the BBTB and inlet manifold actually worked against the MAF conversion. My chip was the "stock" one ~ designed for cars without any modifications at all.

Overall, though, I was pretty happy with the outcome. I can't wait to get my WAR chip mapped. That is where I should get some gains, as I can map for my mods and not be tied to a generic tune.

[e301988325i]

for info the M20 AFM is 38 x 48mm = 1824sq/mm
for info the M30 AFM is 38 x 72mm = 2735sq/mm
M20 60mm TB = 2350sq/mm - spindle shaft is actually 8mm dia.
M20 64mm TB = 2700sq/mm - 15% bigger in area

I hadn't worked that out before, makes interesting reading.

edit - improved accuracy based on actual 8mm TB spindle shaft, and notice how the big bore M20 TB is so close to the M30 AFM.

Here's one I made earlier - going out to fit this in a minute, notice how close in area it is to my M30 AFM!

[Speedtouch]

You bored it out yourself?

[e301988325i]

That was the easy bit, making the butterfly at 4 degrees required some thought!

[Simon13]

thing is standard 2.5 inlet system is good for up 220bhp? Its the exhaust side of things where the tuners got the power from

[E30BeemerLad]

does going mad with the throttle body on a M20 reduce low down grunt?

[e301988325i]

does going mad with the throttle body on a M20 reduce low down grunt?

Short answer is no, Oakey's M20 on throttle bodies (massive inlet area) made monster low-mid torque. Running a higher lift/duration cam too which was odd. His six branch has primaries about 2/3 as long as mine, and quite a bit smaller in diameter, possibly a magnex. The bends in the btb's primaries are 'acute', meaning they reduce the exhaust flow expected of a tube that size, so maybe there is not as much difference as it first appears.

If you mean my BBTB, at 15% larger, I wouldn't have thought it would have a huge affect aywhere TBH. But every little helps and I like to tinker!

[e301988325i]

thing is standard 2.5 inlet system is good for up 220bhp? Its the exhaust side of things where the tuners got the power from

Obviously that's a N/A tuning figure, but which parts do you mean exactly? I'd be interested to hear any knowledge you have on making M20's go better

[eta]

I hope the BBTB works out better for you than it did for me. Although I will refit mine when I get the exhuast sorted out which is delayed a bit as the wife car had a big bill which I had to pay.

[e301988325i]

Most of the time I run on lpg which has a seperate ECU to constantly control fuelling. The standard motronic ECU cannot add extra fuel if you add extra air flow, it needs a new map/chip to do so, which is why after installing my BBTB and BTB manifold the car will run lean on petrol after 5000rpm. I will have to get a new map/chip made for my car.

When I was last at the dyno, the operator did two runs, one with the air temperature sensor in ambient, the other with it in the engine bay, 20 odd brake more was registered with it in the engine bay.

Does/did your car actually feel 18bhp slower?

[Simon13]

With all the greatest respect to oakey his car isn't making much more torque than my Alpina engine. The only thing better than a stock 2.5 inlet is diblas throttle bodies imo

The best bit on oakeys engine is the alpina bottom end which are different to all the diy 2.7's as they use 135mm rods and custom pistons. No vernier needed

Alpina engines are quoted @210bhp and 213lbs. My rebuilt one is making this power. The inlet side of the engine is the same as a stock 325i. The inlet ports on the head are tickled a bit.

The real work alpina did was on the exhaust side, they opened the exhaust ports right out, fitted their 6 branch and large 50mm bore exhaust system. 325's use 44mm exhaust

The chambers in the head are reshaped also to hemi shape instead of bmw's swirl type from factory

[reggid]

With all the greatest respect to oakey his car isn't making much more torque than my Alpina engine. The only thing better than a stock 2.5 inlet is diblas throttle bodies imo

The best bit on oakeys engine is the alpina bottom end which are different to all the diy 2.7's as they use 135mm rods and custom pistons. No vernier needed

Alpina engines are quoted @210bhp and 213lbs. My rebuilt one is making this power. The inlet side of the engine is the same as a stock 325i. The inlet ports on the head are tickled a bit.

The real work alpina did was on the exhaust side, they opened the exhaust ports right out, fitted their 6 branch and large 50mm bore exhaust system. 325's use 44mm exhaust

The chambers in the head are reshaped also to hemi shape instead of bmw's swirl type from factory

Simom i would reconsider my comments about the dbilas intake until reading this

http://www.e30clubsa.co.za/forum/index. ... -m20-325i/

Spot on about the exhaust, the pressure waves generated from exhaust are 10 times stronger than that of the piston pull itself, use these and you can make some good improvements.

[Simon13]

What a great read! Doug do you know what cam this guy was running?

[reggid]

What a great read! Doug do you know what cam this guy was running?

It was a great read and it goes along way to confirm what i thought, the runners are too big and too short on the dbilas.

I sent Stephen a PM and he said it is a catcams 1300537 which is a 288/272. It looks like it is designed for a turbo if i understand correctly meaning the exhaust side is quite a bit smaller in lift and duration with wider lobe separation to limit overlap. His comments on it compared to the schrick 288 are

"This is a really sweet cam, and for me totally outperforms the 288 Schrick I was previously using. It dies at the top over 6300rpm where the 288 would pull easily through to 7000 and I lost 2 kw at the top, but the real-world driving characteristics more than make up for that as the mid-range punch is far superior"

This is not the first time i have seen disappointing results with the dbilas, this thread also shows the results which were a little dissapointing given the spec of the motor.

http://www.r3vlimited.com/board/showthread.php?t=120664

[AlpineAde]

Thanks for the links, Doug. Excellent stuff! I've always looked at the Dbilas stuff with much lust but on the face of what you've posted I feel a whole lot less of it now. It just looks like too much hassle with something that isn't really thought through in the details. In summary, then, too short and too big (45mm)? I'm really glad I stuck with my OEM manifold I must say. The more I read about the standard item the more impressed I am with its design.

[reggid]

Thanks for the links, Doug. Excellent stuff! I've always looked at the Dbilas stuff with much lust but on the face of what you've posted I feel a whole lot less of it now. It just looks like too much hassle with something that isn't really thought through in the details. In summary, then, too short and too big (45mm)? I'm really glad I stuck with my OEM manifold I must say. The more I read about the standard item the more impressed I am with its design.

A quick check in my references shows 34-38mm bore and 350-400mm length from valve to runnner entry is about where you want to be.

[Simon13]

BUT* from reading the diblas web side i thought you could spec bore size and length of pipe to help match to the cam your running. As from my limited knowledge proper tuned engines have the inlet,cam and exhaust all matched together somehow to get the best results?

This is why i went for a 284/272 schrick with my Racing dynamics exhaust manifold, as i knew they used 284 cams on their engines. Sadly it was just an educated guess as i didn't know any other info on the cam they used, but the engines gives nice curves on the dyno

[AlpineAde]

Simon, do you have a link? I'm damned if I can find that.

I've been hunting around here:

http://www.dbilas-dynamic.de/dbilas_eng/index.htm

And in the FAQs.

[reggid]

BUT* from reading the diblas web side i thought you could spec bore size and length of pipe to help match to the cam your running. As from my limited knowledge proper tuned engines have the inlet,cam and exhaust all matched together somehow to get the best results?

This is why i went for a 284/272 schrick with my Racing dynamics exhaust manifold, as i knew they used 284 cams on their engines. Sadly it was just an educated guess as i didn't know any other info on the cam they used, but the engines gives nice curves on the dyno

I heard that aswell but emailed dbilas and got a different story......you can buy the adapter seperate and DIY

[oakey]

Interesting stuff. I'm gonna be getting my trumpets opened out as they're only about 30mm at the bottom end, get my airbox on there with a single filter and me new exhaust and see what difference it makes to mine.
The main difference I noticed before and after the itbs was the low end and midrange grunt (which admittedly I wasn't really fussed about). It picks up from 2500rpm and goes, unlike most 'cammed' m20s that don't get going until 3500-4000rpm

[e301988325i]

A quick check in my references shows 34-38mm bore and 350-400mm length from valve to runnner entry is about where you want to be.

I'd definitely agree with that for a road car.

To warrant short 45's on a 2.7 you'd want one of the mental 332/324 degree cams, running to 8000rpm, these cams are available from dbilas I believe interestingly enough.

http://www.dbilas-dynamic.de/dbilas_eng/index.htm

[e301988325i]

products, perfromance camshafts and accessories, performance camshafts, bmw, then scroll approx half way down for m20

[Simon13]

yeah thats for racing only i'd say, everything would need to be uprated! esp rockers for some 8000RPM action!

[AlpineAde]

8000rpm!! That would be stunning! Big money billet rockers needed there definitely.

[bss325i]

What a great read! Doug do you know what cam this guy was running?

288.

After reading that thread it seems to potentially be a one off.

There is also no mention of what length runners they are other than +/-15cm.

AFAIK there a 3 different length runners available when purchasing an M20 dbilas set up new. That guy bought his used.

[tomson]

Isnt Scott Players 2.8 running the Dbilas ITB's? That thing makes huge power for an M20!

[bss325i]

What a great read! Doug do you know what cam this guy was running?

288.

After reading that thread it seems to potentially be a one off.

There is also no mention of what length runners they are other than +/-15cm.

AFAIK there a 3 different length runners available when purchasing an M20 dbilas set up new. That guy bought his used.

Ooops, i didn't read this page!

[bss325i]

Isnt Scott Players 2.8 running the Dbilas ITB's? That thing makes huge power for an M20!

260bhp apparently

[reggid]

Isnt Scott Players 2.8 running the Dbilas ITB's? That thing makes huge power for an M20!

overlay oakeys 2.7 and see the 2500-5500rpm torque differences and this i understand this was without BTB2 which works best in this rpm band so while it makes good topend it sacrifices alot of midrange with the bore and length of runners

[oguz327]

Interesting reading

[Simon13]

would the bad result be more down to running a turbo style cam, which isn't the sort of cam to run with itbs i'd expect?

[Steve]

Isnt Scott Players 2.8 running the Dbilas ITB's? That thing makes huge power for an M20!

260bhp apparently

Then ask him, how much money he spent to get 260bhp out of an M20

[tomson]

Isnt Scott Players 2.8 running the Dbilas ITB's? That thing makes huge power for an M20!

260bhp apparently

Then ask him, how much money he spent to get 260bhp out of an M20

Yeah, I know, its crazy !