MyE28.com DEV

Does the stock cam have a boost/hp limit where it just won't
make any more power at high rpm?

Or is it just more boost = always more power?

How about if it somehow got advanced a tooth so it has
a hard time reving out even with a ton of boost up there?

The cam determines the shape of the torque curve. A stock b34 cam has a torque curve that start falling off above about 4500 rpm and really starts falling after 5k rpm. Given a motor that receives constant intake (boost) pressure, a turbo motor will have the same curve shape, only with larger numbers.

The b35 cam makes it fall off slightly later. I'm not sure where the point is that cam won't net more high end power and you need to either add more boost pressure as revs rise or change the intake tract via port/valve work or other alterations.

Jeremy

Shadow wrote:Does the stock cam have a boost/hp limit where it just won't
make any more power at high rpm?

Or is it just more boost = always more power?

How about if it somehow got advanced a tooth so it has
a hard time reving out even with a ton of boost up there?

My m30s always carried the HP out to and past 6000rpm. An advanced cam would certainly kill the top end.

Dyno of same motor at 14.5psi and 19psi.

Dang...ok thx.
I'm just trying to figure out if it's not a motor problem I'm
having. Was thinking of putting in my 288 schriek maybe.

@ 5,000rpm, and 21psi it does 422tq in *3rd gear
Then @ 6,000rpm, and 24psi it goes down to 370tq about...

afr where perfectly flat too and constant timing.


Probably a megasquirt problem I guess..

At 5000 rpm you are much closer to your torque peak than at 6000 with a stock cam. There is nothing wrong with the engine based solely on that.

There's about a 20tq dip in between 5,500 and 6,000 that
goes back up. I'm going to pump it up 2psi more up there see
if it feels better. F-it. In my old m20 it would rev out to 7,000 still making power just seems weird that the m30 isn't.

Plus it was losing rpm signal on the dyno.

More boost wont solve anything.

Comparing torque in 3rd gear to torque in 4th or 5th gear will always yield a lower figure in the higher gear. The very reason for lower gears is to make more torque via gear multiplication.

As Kyle said more boost will not change the engine characteristics. Also a cam grind for a NA engine (lift and duration) may not be optimal for a FI engine (duration). So your Schriek may or may not give you what your want.

More boost will only help if you can keep IAT down and you're not knock limited on the type of fuel you're running. The turbine and manifold can also choke up at a certain point. That may be why you can't move any more air mass through the engine despite increasing boost on the intake side. You may have a cork in the hot side of things.

ok.
That's on the list now.
1) noise suppressor to megasquirt power
2)ls2 coil on plug
3)exhaust pressure gauge.

Coldswede wrote:Comparing torque in 3rd gear to torque in 4th or 5th gear will always yield a lower figure in the higher gear.

On a dynojet a lower gear reads less power but not by much.

On a dynojet a lower gear reads less power but not by much.

Well, you might get that reading somehow, but that is physically impossible.

1) noise suppressor to megasquirt power

What issue are you having?

My electronics lower voltage down to a min of 12.9v..
and that's where the dip and loss of power is occurring.

I've marked 5,500rpm.

Some of the runs, the dyno lost tach signal so it's been suggested to me to run a noise suppressor
and switch out the msd for stronger spark. ls2 COPs.

Earlier went and did 290kpa up there, and it still was slowing down.
Faster! but it just doesn't want to keep pulling.

Coldswede wrote:

On a dynojet a lower gear reads less power but not by much.

Well, you might get that reading somehow, but that is physically impossible.

Yeah I know.
Here's some good quotes explaining why it's true.
http://ls1tech.com/forums/dynamometer-r ... mbers.html
Most of these guys lose 10-20hp depending on gear ratio
in 3rd vs 4th *1:1 but it's so little power.

I upgraded my valve springs and went with heavy duty rockers after breaking rockers several times.It now revs past 6k with no problems, stiffer springs do help.
marc

You're running 20 degrees of advance at 1.6 bar? Seems like a lot. Like about twice as much as I would think would be good. Must be on e85?

Any lower there is a noticeable power loss.
at 10* like you say the manifold and turbo glow.
and is also very slow.

cam timing off?! maybe retarded a tooth

Shadow wrote:Any lower there is a noticeable power loss.
at 10* like you say the manifold and turbo glow.
and is also very slow.

Running pump gas or e85?

91 and meth injection.

winfred wrote:cam timing off?! maybe retarded a tooth

God I wish this was it. Waiting on an e30tech guy to finish his
cam sensor wheels and check out the cam timing while im in there.

The dyno was losing rpm signal and that was the only run
it did not. So most likely some sort of electrical... ?

Shadow wrote:@ 5,000rpm, and 21psi it does 422tq in *3rd gear
Then @ 6,000rpm, and 24psi it goes down to 370tq about...

370ft*lbs at 6000rpm is 422HP. 422ft*lbs at 5000rpm is only 401HP. And that is with a stock cam? I don't see any problem.

Perhaps I am ignorant to the dynamics of power making
on the m30, but I believe it should be making more power than THAT up top. idk.


Another dumb question.

I have a shchiek 288 but am afraid of low end power
loss and perhaps raising the chances of pinging.

So the question is if I get an adjustable cam gear and max out the retard, (anyone done this?)
how much more RPM do I get before the torque starts to drop?

Ordered these coils just in case it's an ignition thing.
Going to run them wasted spark.
http://www.aemelectronics.com/high-outp ... -coil-1240

Coldswede wrote:Comparing torque in 3rd gear to torque in 4th or 5th gear will always yield a lower figure in the higher gear. The very reason for lower gears is to make more torque via gear multiplication.

most dynos reading torque do not account for gear multiplication. the torque is nothing more than

5252* hp @ wheels / crank rpm.

to get "real" torque at the wheels you need

5252*hp at wheels/ wheel rpm.

the much lower wheel speed compared to the engine speed is where the gear multiplication is borne but most dynos dont use this though it is possible but less valuable for tuning

Shadow wrote:Perhaps I am ignorant to the dynamics of power making
on the m30 but, I believe it should me making more power than THAT up top. idk.


Another dumb question.

I have a shchiek 288 but am afraid of low end power
loss and perhaps raising the chances of pinging.

So the question is if I get an adjustable cam gear and max out the retard, (anyone done this?)
how much more RPM do I get before the torque starts to drop?

Ordered these coils just in case it's an ignition thing.
Going to run them wasted spark.
http://www.aemelectronics.com/high-outp ... -coil-1240

I'm running an old schrick 280/284. Adding a larger cam does not make your engine ping, higher compression will do that or excessive timing.
The larger cam will make a huge difference especially with a tubular manifold.

Thanks for posting G&T.

How does it feel vs stock on the low rpm drivin around town
aspect?

Here's the dyno btw it kinda emberessing.
After 5.5k it just stops reving.....

Re-dyno this month with the new coils and if that doesn't fix then cam time.