Lose of power at higher rpms

[digger]

Guessing when you say "billet" cam, it's an Ireland grind - as they advertise them as billet, but are just new castings that are ground to IE's specs.

billet is apparently used interchangeably with non regrind these days....

[ForcedFirebird]

Can you post or PM the timing table? There might be too much timing at peak TQ, which could cause pre-detonation.

Also, not sure who rebuilt your AFM, but they should be calibrated for spring tension after rebuild. I have seen them freshly rebuilt and needed 4 clicks on the spring to get the AFR proper (shouldn't be an issue with the custom chip, though). Not a bad idea to pop the AFM cover off and make sure the wiper isn't going off the track (seen this in rebuilt AFM's as well).

Guessing when you say "billet" cam, it's an Ireland grind - as they advertise them as billet, but are just new castings that are ground to IE's specs.

FWIW, we have an m20 here at the shop with more compression and it would ping on occasion with when it's hot out (or cheap gas) with a 272/284 dual pattern cam. Pulling a few degrees at peak TQ remedied it.

A healthy m20 doesn't like much more than about 27° of timing at peak, and they do like to run in the 13's for power N/A.

[digger]

Just as a data point with my similar Bimmerheads engine, I am at 211 whp on my 2.9 Mahle stroker despite a 5800 rpm rev cap glitch on my megasquirt and stock intake mani / throttle / valves. It has the 284/280 cam which isn't as rough as I thought but I would definitely stay smaller on the cam for a DD- even with a good dyno tune it is barely drivable when cold and with my 8 lb flywheel unbearable in LA traffic.

I would personally splurge on a standalone and / or cam gear rather than dealing with breaking in a new cam again, if my engine is where it is and climbing through the stock throttle then an incognito AFM setup with megasquirt should be fine for 200 whp, and I wouldn't want my brand new engine running anything other than a flawless tune. This will also set you up for ITBs in the future.

that cam has an earlier IVO and later EVC than a schrick 288 but less lift at TDC, it has a fair amount of overlap and is a slow ramp profile which is never good for light throttle and smooth idle, its very gentle on parts though.

[whitebulat22]

Just as a data point with my similar Bimmerheads engine, I am at 211 whp on my 2.9 Mahle stroker despite a 5800 rpm rev cap glitch on my megasquirt and stock intake mani / throttle / valves. It has the 284/280 cam which isn't as rough as I thought but I would definitely stay smaller on the cam for a DD- even with a good dyno tune it is barely drivable when cold and with my 8 lb flywheel unbearable in LA traffic.

I would personally splurge on a standalone and / or cam gear rather than dealing with breaking in a new cam again, if my engine is where it is and climbing through the stock throttle then an incognito AFM setup with megasquirt should be fine for 200 whp, and I wouldn't want my brand new engine running anything other than a flawless tune. This will also set you up for ITBs in the future.

[digger]

you can try contacting tinkerputzer or nando

[LowR3V'in]

i would love to see the power shifting around on a dyno fucking around with cam timing.
dyno time isn't too expensive i would do it, but, m30.

How much did those guys gain about by doing that, digger?

[Cabriolet]

Digger, thank you. i never knew that is was off by that much.

[digger]

I don't have an adjustable cam. It's set to factory cam settings.

its probably a good investment, for example there are a few members who found that with the 284/272 cam that several degrees of retard made more power than as installed with factory marks. when i plotted out the cam it showed that the factory gear would mean the cam installs advanced alot so retarding the cam from the factory marks would mean it is installed as recommend by schrick

[Cabriolet]

I don't have an adjustable cam. It's set to factory cam settings.

[redlightpete]

Did you set the cam timing by measuring the valve/cam lift? Maybe the cam timing is more advanced than optimum for top end power.

[Jaxx_]

I like to be at 12.5 or 12.3 for an NA street car, but I'm paranoid. Remember your O2 sensor is an average of all cyls. In general you tend to not see much of a difference in power being a little richer than needed, but it's safer. Timing is where you make your power. With that said, in my (limited) experience these motors will handle leaner conditions (~14.0 at WOT) in stock form without issue.

It really may be that the cam you have is not great, but I am not well informed on cam profiles for the M20 and what exact profile your 272 has. I agree with digger regarding cam timing--if you shaved the head you're advancing the cam timing as the chain length is shorter.

Regarding ignition timing, if your tuner at or over 30 degrees by 3-4k rpm I'm sure it's within the ball park. If not, I would add timing 2 degrees at a time until you stop picking up good power--unless you have some sick coated bearings and wanna run on the ragged edge with pump gas

[LowR3V'in]

oh i see. :(

[digger]

you think he can send you that timing table?
my m30 picked up some hp after 5k with *2 more advance.
*2 more before 5k would lose like 7hp so it's a fine line.
looks like you're missing 20hp though

also i would go with a bigger cam it's not bad. i got a 293 or something like that
from cat cams. feels normal.
has alittle bit of cam sound in the exhaust but isn't felt driveabilty wise.
wish i went with their 300 for more revs.

yours is a turbo cam, it has wide lobe centres and small exhaust lobe so the overlap is relatively small. Also the M30 is a bigger engine which tames duration

04.041.012 from dbilas looks like a option https://dbilas-shop.com/en/engine-va...mshaft?c=12007

[LowR3V'in]

you think he can send you that timing table?
my m30 picked up some hp after 5k with *2 more advance.
*2 more before 5k would lose like 7hp so it's a fine line.
looks like you're missing 20hp though

also i would go with a bigger cam it's not bad. i got a 293 or something like that
from cat cams. feels normal.
has alittle bit of cam sound in the exhaust but isn't felt driveabilty wise.
wish i went with their 300 for more revs.

[digger]

working with what you have i would check cam timing to see if its advanced. with a small cam like that it will want a bit of retard to it if you want it be happy pulling to 7k.

AFR look fine, the timing probably still needs to be optimized.

you could probably conceal a PNP MS setup pretty well if its purely visual, even a gutted M30 AFM to make it look period correct

its true that a stock manifold doesn't like much overlap it makes idle and low speed suffer, and that will be the case if you go upto a 288 but there is some middle ground.