Exhaust X-pipe And Intake Runner Length Experiment. Bmw M3.

nilsp

Member
Hi,

Looking for advice to understand my results after a little dyno session which we didnt have time to do more.

Basic;
Bmw e30 m3 s14 engine, a little NA 4 cyl which isnt very powerful compared to the big v8`s and stuff.
Stock 2.3 liter was 200hp, a detuned engine for road cars sinc they really were made for racing homologation in the 80`s.

My engine is stroked to 2.66 liter, and built for road use, not for max at very high rpm.
All parts in engine is top quality stuff,and all can handle 9000 rpm, but as mentioned, its a road car for now.
Got bigger camshaft on the shelf. These only 10 and 12 mm lift.

Thing is, it has a big torque dip, which really isnt as bad as it seems on dyno papers, and its stronger with less than 100% throttle.
Anyway I have done some testing on moving the x-pipe a little to see how it really affects the powerband.

Secondly, after a little research and trying to learn stuff around this, I discovered that my engine theoretically wants quite a bit longer intake.

Since I`m running the m3 classic carbon intake, which is only made in 2 sizes these days, I tried installing some alu air horns in there.
Problem was to make them sit. I didnt want to superglue them first thing after all, so they fell out, or 2 of them, every time.
-but I think it looks promising.
Added photo shots of dyno data, with some comments on.

After showing these in another forum, a guy mentioned anti-reversion, which was new to me.

Could that help me? And where should I put it?
Also I consider the x twice the distance? But didnt get to test it.

I need to rebuild the whole front of the exhaust system when fitting into car again next weeks anyway!

Btw, 4-2 tri-y header, long primaries, and x-pipe placed 24-35-38 cm behind tri-y meets.

All comments welcome!

Dyno numbers hp, and nm.
 

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first let me state, thank you for posting the pictures and dyno results

could you give us some idea as too,
the cam timing, (lift ,duration)?
cylinder head flow rates,?
static compression ratio,?
ignition advance curve,?
intake valve diameter?
intake port cross sectional area?
intake runner length?
exhaust valve diameter?
, and header primary tube diameter?
and length?
fuel/air ratio every 1000 rpm?
exhaust back pressure in the collector every 1000 rpm?
intake plenum vacuum every 1000 rpm?
with that data we can stop random guess work,
and have at least some facts to work with,
to make a semi logical guess as to what changes might help.

guessing is fast and easy, getting a few facts and working out the details is a bit harder but more productive

http://www.wallaceracing.com/Calculators.htm


http://garage.grumpysperformance.com/index.php?threads/calculating-header-design.185/

http://garage.grumpysperformance.com/index.php?threads/building-custom-headers.961/


http://garage.grumpysperformance.com/index.php?threads/header-dimension-calculator.15013/

http://garage.grumpysperformance.co...ful-exhaust-valve-size-and-header-info.11265/

https://www.speedwaymotors.com/Dyna...Bz6emuEjF4N1k5y0bOy7WTF0w3YWiZOoaAiIGEALw_wcB

http://garage.grumpysperformance.com/index.php?threads/dyno-testing-headers.3529/

http://garage.grumpysperformance.com/index.php?threads/calculating-required-exhaust-pipe-size.11552/

http://garage.grumpysperformance.co...-guys-that-just-slap-on-factory-headers.3155/
 
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So I see 320 Newton Meters torque .
That converts to 236 Foot pounds torque that I relate to better here in the USA.
Just 4 cylinders.
A V8 of same bore stroke parameters torque will be double.
472 Ft/lbs.
 
It's making 1.97 Horsepower per cubic inch.
It's 162.29 ci.
2.66 Liters.

I see about 320 Hp on the graph at 7500 rpm.
 
If this was a V8 engine same bore and stroke parameters it would be a 324 ci V8.

It's high output.
To get a big leap in torque it's going to take Turbo Boost !
 
first let me state, thank you for posting the pictures and dyno results

could you give us some idea as too,
the cam timing, (lift ,duration)?
cylinder head flow rates,?
static compression ratio,?
ignition advance curve,?
intake valve diameter?
intake port cross sectional area?
intake runner length?
exhaust valve diameter?
, and header primary tube diameter?
and length?
fuel/air ratio every 1000 rpm?
exhaust back pressure in the collector every 1000 rpm?
intake plenum vacuum every 1000 rpm?
with that data we can stop random guess work,
and have at least some facts to work with,
to make a semi logical guess as to what changes might help.

guessing is fast and easy, getting a few facts and working out the details is a bit harder but more productive

http://www.wallaceracing.com/Calculators.htm


http://garage.grumpysperformance.com/index.php?threads/calculating-header-design.185/

http://garage.grumpysperformance.com/index.php?threads/building-custom-headers.961/


http://garage.grumpysperformance.co...ful-exhaust-valve-size-and-header-info.11265/

http://garage.grumpysperformance.com/index.php?threads/dyno-testing-headers.3529/

http://garage.grumpysperformance.com/index.php?threads/calculating-required-exhaust-pipe-size.11552/

http://garage.grumpysperformance.co...-guys-that-just-slap-on-factory-headers.3155/
Data your looking for are $10,000 cash Dyno sessions Grumpy.
 
Another perspective...
My last Pontiac 455 v8 punched .030"over I engine simulated recent at 592 Horsepower.
It made 1.28 Hp per cubic inch.
At 1.97 hp/ci it would make 910 Horsepower normal aspirated no power adder.
 
If this was a V8 engine same bore and stroke parameters it would be a 324 ci V8.

It's high output.
To get a big leap in torque it's going to take Turbo Boost !

Hi,

Thanks for your view.
Yes, its high output, and Im not expecting any higher max torque than this.
Its actually between 325 and 330 nm, on 400rpm/sec pulls.
Made one final,last pull slower, 250 rpm/sec. 336nm and 331 hp.

This equals ve of over 120.
We didnt log much on the dyno itself, only egt. The rest in the engine management system.. which I didnt get data from now.

What Im looking for is making that torque dip a little better, and/or ,to move top hp up a few hunded rpm which would make good power.
 
first let me state, thank you for posting the pictures and dyno results

could you give us some idea as too,
the cam timing, (lift ,duration)?
cylinder head flow rates,?
static compression ratio,?
ignition advance curve,?
intake valve diameter?
intake port cross sectional area?
intake runner length?
exhaust valve diameter?
, and header primary tube diameter?
and length?
fuel/air ratio every 1000 rpm?
exhaust back pressure in the collector every 1000 rpm?
intake plenum vacuum every 1000 rpm?
with that data we can stop random guess work,
and have at least some facts to work with,
to make a semi logical guess as to what changes might help.

guessing is fast and easy, getting a few facts and working out the details is a bit harder but more productive

Grumpy;

Thanks for informative links,
Was going to answer most of your questions, just needed a little more time


Trying do details from the top.

Cams 312 degree intake, 12mm lift. Timing 98
Exhaust 292, 10mm, timing 100.

Head flow appr 320 cfm at 12mm. Exhaust 214cfm
at 10mm.
Valves intake 2 x 39mm exhaust 2 x 32.5mm.
4 x 50 mm throttle bodies, butterfly, into double 30mm ports,all the way to seat.

Intake lenght valve to runner, around 45cm I think.

Compression 11.7.

Primary headers 50mm id, 55 to 65 cm lengths.
Collectors after primary, in front of x, 63mm.

Ignition advance 20 to 25 degrees.

Afr 13 to 12.5

No backpressure sensors Im afraid, but maybe I should have that. One on each collector pipe before x?

Vacuum.. dont have them here now, but last year there was nothing on it, except a little drop just before peak hp.
 
Engine back home today.
Checked valve clearances and cam timing.
Found exhaust cam timing at 98.5, should be 100.
Changed it to 101 to see what that could do.

index.php
 

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Can see the cams. Low lift, high duration.
index.php
 

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Install the engine in the car.
Then test drive.
It's a High strung 4 cylinder.

Might have to change your past driving style to suite the new powerband.
 
Install the engine in the car.
Then test drive.
It's a High strung 4 cylinder.

Might have to change your past driving style to suite the new powerband.
Yes, I will.. in the process of installing it now.

Just considering if I should double the collector length, to better fit under the car, and possibilities for anti-reversion chamber in front of the X pipe. Sounds like a bad idea?
The collector length is 34cm now (13,4») Doubling it shouldnt be a big risk as it should hit the same harmonic?

Where would beckpressure sensors be useful in this system? One in each collector?
 
Yes, I will.. in the process of installing it now.

Just considering if I should double the collector length, to better fit under the car, and possibilities for anti-reversion chamber in front of the X pipe. Sounds like a bad idea?
The collector length is 34cm now (13,4») Doubling it shouldnt be a big risk as it should hit the same harmonic?

Where would beckpressure sensors be useful in this system? One in each collector?
Some or all the Exhaust system theories are not practical on most production body cars.
Just no room.
People lack the extreme fabrication tools.
Experience.
So on.

Stuff works.
Best to me in open bodied race car destined for road race.
 
Even if you had a Turbo that put out just 4-5 psi you likely exceed anything that is theoretically possible with N/A exhaust scavenging.
How much time and money do want to put in ?
 
Turbo Boost is typical done with 11.0:1 static compression and 230 @.050 duration cams today.
Basic outlay to double or quadruple power output.

Just does not work with Nitromethane mixes 80-90%.
Blow the heads right off the engine.
 
Even if you had a Turbo that put out just 4-5 psi you likely exceed anything that is theoretically possible with N/A exhaust scavenging.
How much time and money do want to put in ?
Spent way to much already.
Now is just installing it again.
But I need to rebuild the front end of exhaust system to fit the car anyway, the angles wasnt correct when in dyno, that was q quick fix to adjust stuff.
Its just a matter of cut and weld now.
The backpressure stuff would cost a little, but my standalone ecu system has capabilties for more, so its just a few nipples to connect a sensor after all.

And dyno time etc is free, my brother has the dyno.

As you understand, I`ve already spent way to much time on this stuff
But its fun, and very learningful for me.
 
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