big cams - hotwire AFM vs throttle position.

[roadsailing]

Quick one,

I'm planning on putting huge cams (somewhere between 280 and 300 degrees) in my 4AGE, but this isnt a question specific to that engine.

AFAIK MAP sensing of engie load is practically useless in this sort of application and I will have to use throttle position as a load input.

Would I be better off using a fairly free flowing hotwire airflow meter?

[tandy ass]

Theorising here, wouldn't an AFM be better as far away from the engine as possible?

This would smooth out the intake charge pulses as much as possible due to length of intake pipe. I'd also be curious if the ECU "averages" a pulsing intake charge to get the correct flow....

[roadsailing]

well the hotwire will have some thermal mass, so i guess the fluctuations in wire temperature/resistabce would be less severe than the pressure fluctuations in a MAP sensor (that doesnt have the orifice/fuel filter trick done to it), if they were severe it would be a simple exercise to average it out using digital or analog filtering to create a stable output voltage.

[Billzilla]

Ditch any AFM's, just use TPS & revs to sense load.
I did that on mine, with similar cams, and it drove just fine. You need a goodly amount of load points below about 4,000rpm though to make it drive nice.

[roadsailing]

cheers bill, i was wondering if it would make much difference in tuning and running (IE with TPS only if you WOT it does it make it run rich etc) i dont understand engine management anywhere near as much as i want to.

mind if i pick your brain a little about your old setup in regards to drivability?

[Billzilla]

cheers bill, i was wondering if it would make much difference in tuning and running (IE with TPS only if you WOT it does it make it run rich etc) i dont understand engine management anywhere near as much as i want to.

mind if i pick your brain a little about your old setup in regards to drivability?


Yeah, ask away.
The mixtures at any throttle setting and any revs will only be what you program them to be from the fuel map - They will be a rich or as lean as you like.

[roadsailing]

I might just ask here, as other people may be able to benefit from the answers (i apoligise if you have answered some of these millions of times) I have been reading up on your site, and have read about your setup elsewhere, but i wont write up any half remembered info.

as far as your setup went:

what duration/lift were your cams?

what static CR was it running (after it went into the clubman)

power output/useable power speed range?

did you lose noticable power/torque over the RPM range compared to the standard cams?

fuel economy?

additionally:

I think i'm starting to realise, if you know Throttle position and RPM, you basically know engine load, but this still seems like a rough way to do it to me, need to consider it more.

Also, is there much advantage in running different profiles on each cam? (for example 300 degree inlet, 280 exhaust)

and one last one, is it worth keeping near-standard lift and relying on cam duration to make power? or are shimless buckets/shim under buckets less of a pain to adjust than i am assuming?

cheers

[Billzilla]

I might just ask here, as other people may be able to benefit from the answers (i apoligise if you have answered some of these millions of times) I have been reading up on your site, and have read about your setup elsewhere, but i wont write up any half remembered info.

as far as your setup went:

what duration/lift were your cams?

246° at 0.050" lift, 0.380" lift.



what static CR was it running (after it went into the clubman)

Not sure, because when I first built the engine I made a mistake and the compression ended up way too high, so we ended up having to mill the tops of the pistons and them round them off by hand. Very ugly!
I think it's low 11's at the moment but we had to destroy the squish areas so it doesn't go as hard as it did when first put together. I'm putting in new pistons in it in the next few months that'll fix that, so it'll go very hard again.



power output/useable power speed range?

It'd idle at 1050rpm okay, not too rough. It'd pull from about 1700rpm in any gear. It'd be quite driveable from 2100rpm, jump up in power (with a big increase in induction noise!) at about 3400rpm, and go beserk at 6000rpm.
I set the rev limiter to 8400rpm to be conservative, but the logging on the Motec told me that it ran to 8690rpm once - That was the 200rpm 'soft limiter' on the Motec and the 3kg flywheel. :)




did you lose noticable power/torque over the RPM range compared to the standard cams?

I don't know, I've never owned a standard 4AGE. I'd say below about 2100rpm the stock engine would be better, above that mine was better.
Though it had a bit of a dip in torque between ~3000 - 3300rpm that I could never completely get rid of.



fuel economy?

Depends on how I drove it, but normal driving in traffic around town gave me about 30mpg and the best I got was 42mpg on the highway. That's very good I think!
Using 365cc/min 4AGZE injectors I got up to about 65% duty cycle at full throttle/max torque I think.




additionally:

I think i'm starting to realise, if you know Throttle position and RPM, you basically know engine load, but this still seems like a rough way to do it to me, need to consider it more.

I had 250rpm load points below 4000rpm in the Motec, and TPS load points of 0%, 1%, 2%, 5%, 7.5%, 10%, 15%, then 5% up to 50% and then every 10% from there. Overkill for sure! But with the Motec you can add pretty much as many load points as you like to smooth things out. I also have feedback from the Lambda sensor so it was easy to tune anyway.




Also, is there much advantage in running different profiles on each cam? (for example 300 degree inlet, 280 exhaust)

There can be minor improvements, but it's probably not really worth mucking around. But if you want to, I'd go for a little more duration on the inlet and a little more lift on the exhaust.



and one last one, is it worth keeping near-standard lift and relying on cam duration to make power? or are shimless buckets/shim under buckets less of a pain to adjust than i am assuming?

cheers


You only adjust the shimless (1SZ) bucket maybe once every 40,000kms or so, so it's not big deal really.
But if you use cams small enough to keep the shim-overs, that makes life a little easier that way.

[roadsailing]

thanks bill!

mine doesnt make any noticable power until about 4, but havent compared it to too many other 4AGE sprinters so if anything bigger cams would be better all over the place (after management, quads, extractors tuning etc)

[Billzilla]

thanks bill!

mine doesnt make any noticable power until about 4, but havent compared it to too many other 4AGE sprinters so if anything bigger cams would be better all over the place (after management, quads, extractors tuning etc)


Maybe.
It's not one simple fix, and don't forget that they're still only 1600cc's and so if you want a lot of power (you can get it!) you'll have to sacrifice some low end power.
The manifold lengths are critical .... ;)