Engine Performance?

[crashmy911]

Engine is 3.0 with 10 3 to1 compression race cams twin plug individual throttle bodies. Trying to determine why it's not making more power. Any suggestions appreciated.

[crashmy911]

[crashmy911]

That is cam profile also running crank fire ignition system and 48 mm ITBs

[crashmy911]

Thought it would pull to 7100 but stops at 6100. Why would this happen?

[RD911T]

I'm no expert, but it has to be your A/F ratio, doesn't it? Are you measuring that when it's on the dyno?

[crashmy911]

It's being minipulated by tuner on dyno .

[crashmy911]

How can you tell if cam isn't set right or if exhaust is causing bottle neck?

[Steve@Rennsport]

There are MANY reasons why its short on power and some of them are:

1) Exhaust system design

2) Cam timing

3) Ignition timing

4) Fuel mapping (AFR's)

5) Injectors mis-sized (duty cycles beyond 80%)

6) Internal drag (many causes)

7) Rings not seated (leakdown tests show this)

8) Heads cannot flow sufficient air to support engine

9) Insufficient octane (I see evidence of possible detonation)


This should help get you started on the process.

[crashmy911]

You see evidence of possible detonation? Maybe u should try another tuner? Any suggestions on east coast?

[crashmy911]

Sorry maybe I should try a different tuner.

[crashmy911]

Injectors are 30lbs. I think.

[crashmy911]

Anyone want to comment? Could use any info.

[jpnovak]

Hard to comment with one line phrases and not details on the build. I believe Herr Steve gave a nice list of items you need to describe.

[al lkosmal]

+1..........more info required. Try to summarize all of the pertinent info in one message and I'll be glad to review & comment.

regards,
al

[crashmy911]

I'll start another thread with all the information needed to figure out problems. Will get other info from tuner Monday. Thanks

[Edelweiss]

Dear Sirs,

Steve is 100 % correct in all points.

Working on dynos every day I can't see any evidence for detonation in your sheet.

The TDC lift of your cam is good for a static compression of min 11,5 : 1 I would say if the squish is done right 12,5 : 1 is perfect.

With this cam detonation will just come up with very bad fuel, a very restrictive exhaust and a dramatic wrong ignition adjustment.

But !

The more your TDC lift the more your system gets reactive - so inlet plenum and exhaust must cooperate....then and hust then you will see power !

Best reg.

Dirk

[Steve@Rennsport]

Originally Posted by Edelweiss

Working on dynos every day I can't see any evidence for detonation in your sheet.

Hi Dirk,

Looking at some of the dyno traces between 5500 RPM and 6K, I see potential evidence of either detonation or intake reversion which can both cause those dips, especially using that camshaft profile.

Without a LOT more details, its virtually impossible to offer anything further, but its certainly cause for review.

[Walt Fricke]

Here is why my first dyno run looked way too low: the butterflies weren't opening all the way.

So that is always worth a check, especially when you aren't even in the ballpark.

[Edelweiss]

Hi Steve,

i was interpreting it in that way that it is more a pulsing / resonance / mixture effect - also typical on those cams when exhaust is not done right.

For sure you are right - without any more Info it's impossible to say really.

Best reg.

Dirk

[Steve@Rennsport]

Originally Posted by Edelweiss

Hi Steve,

i was interpreting it in that way that it is more a pulsing / resonance / mixture effect - also typical on those cams when exhaust is not done right.

For sure you are right - without any more Info it's impossible to say really.

Hi Dirk,

I too, have experienced the very same things with that cam when the headers/muffler are wrong.

Not many people understand how sensitive these engines are about exhaust systems.