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More Power For My Rally Car...


tomorrowcalling

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Hi All,

 

I use my 2002 as a club rally /hillclimb car.  When I built the engine I was aiming for a 150 Hp but the dyno suggests that I missed by about 20-30 Hp. I'm now on a search for my missing ponies, don't get me wrong it runs really well and was professionally tuned by a well regarded local motorsport tuner so there's nothing actually broken.

 

The engine is 10:1 compression ratio with JE pistons  +1mm oversized valves and a 304° cam.

 

I run a E30 318 inlet manifold with a E30 325 throttle body, and an LInk ECU.  The exhaust manifold is off a 520 which looks to be the same as a Tii one.  I'm restricted on what I can do with the exhaust as I'm RHD.

 

I suspect the issue is the 318 manifold is just not flowing well enough to suit the cam,  does anyone have experience that would confirm that suspicion ?.

 

I'd appreciate comments on my options which seem to be,

 

Change to a twin DCOE 45 setup.  Pros: kits are not that expensive (about $1500), it will but me back into the historic class for some events.  Cons: I like that I can reach in through the window, turn the key and it will start, I may lose some low range driveabilty.

 

Change to DCOE type fuel injection throttle bodies, Pros: should make good power, Cons:  kind of expensive.

 

Change to a Tii inlet manifold, I believe they flow better than the 318, modifying it to take EFI injectors should be within my skill set.  Pros: probably the cheapest option, Cons: Will it make a significant difference?.

 

Build my own inlet system based on motorcycle throttle bodies, it's probably right on the edge of my skill set, the learning curve could be quite expensive.

 

 

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I would go to work with the ECU tuning on a dyno...  spark advance and mixture have a lot of power 

hidden in them on this engine.

 

Similar engine, tuned carefully on a dyno with 40mm DCOEs did 140.  With headers, and 32mm chokes.

 

I do think the headers would help hp, but possibly at the expense of torque.

 

How big are your collector and final exhaust pipes?

 

Also, what are you using for an air filter.

 

 

hth

 

t

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When the car was tuned it was on a Dynapack dyno (hub dyno), the operator is very well respected in local motorsport circles so I don't believe there's huge gains to be made there.

 

I'm using a fairly large K & N filter, K & N suggest it's Ok for 3.0 litres.  Exhaust is 2" with a fairly free flow muffler. (The car's quite loud).

 

The 2" section starts from where the two down pipes join.

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Try a 2 1/2" tailpipe.

 

Or measure your backpressure and see if it's high (and no, I'm not sure what 'high' is!)

 

And try larger primary pipes from the manifold- stock on a 2002 is pretty small.

If you could pack a header of reasonable design in there, it would help- but a bad

one would be worse...

 

The 318 manifold's not fantastic- but its not bad.  Especially for mid- range torque, just like your exhaust...

 

Have you checked the ECU mapping and behavior, as in, your fuel injectors aren't at saturation, etc?

Also, check your o2 readings and timing map- you can run these engines in the high 12:1's with 36- 38 degrees 

of total advance and get real power from that.

I have so much faith in 'reputable tuning shops' that I check their work to see their genius in action!

(as in, hire someone good and then convince yourself that they've done good work)

 

What did you get for a torque curve?  You might be making grunt instead of spinning too the moon- and torque wins races...

 

t

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Possible tuning issues aside, I think changing to a Tii-style manifold from a 320i with a 58 to 60 mm throttle body would flow better.  I read somewhere on this forum that there are some suitable injectors that fit without machining the manifold. 

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Where did it make peak power? Is it in the range you would expect for the cam or earlier? If earlier, it is probably airflow. Was vacuum zero at WOT? What was timing at WOT/peak power? Short timing can hurt across the board. Older design, less efficient combustion chambers usually require more timing to make power.

 

If you can, post the dyno sheet.

 

Rob


Where did it make peak power? Is it in the range you would expect for the cam or earlier? If earlier, it is probably airflow. Was vacuum zero at WOT? What was timing at WOT/peak power? Short timing can hurt across the board. Older design, less efficient combustion chambers usually require more timing to make power.

 

If you can, post the dyno sheet.

 

Rob

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2nd TobyB. Make sure your spark and fuel are correct before you start changing out the parts. Otherwise you just end up comparing unoptimized setup a vs unoptimized setup carrot. As MRForce stated at WOT expecilly at high RPMs you the intake manifold gauge pressure should be close to 0. That would be an easy check to see if there is a problem on the intake side before you head into a tune.

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Using a dyno that reports greater results depends on whether he wants a real power increase or more bragging rights.

Jim, you have some valid points but is the condescension really necessary?  We're all on the same team here.

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