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Dave
9th January 2001, 21:02
Anders
When you had your engine rebuilt , did you replace the cams with longer duration/lift ? If yes where did you get them ?
Cheers Dave

Firefox
9th January 2001, 22:59
Nope.. he didnt..

He just played about with the cam timing/positioning in relation to the crank.

J.

Dave
9th January 2001, 23:21
Using what ? vernier cam pulley's or standard pulley's ?
Also to what settings ? and are they applicable to the standard STI 2 or only the 22B ?
so many questions but I'm trying to find out these things befor I build my new engine .
Thanks in advance Dave

Firefox
10th January 2001, 18:24
They are very good questions.... http://bbs.22b.com/ubb/wink.gif

I just hope you know what you are doing when you build your engine http://bbs.22b.com/ubb/biggrin.gif

J.

pat
10th January 2001, 23:04
Dave,

Anders is running "Group N" cam timing which changes the timing in such a way as to favour mid range torque over top end power. This is, of course, most desirable in a rally car, where the 32mm (GpN, or 34mm on GpA) turbo restrictor limits top end power anyway.

Under "normal" conditions advancing the cams will improve the mid range at the expense of top end. The "bible" says that you can knock the cams out by 3 teeth before there may be valve to pistonor valve to valve interference. IIRC, there are 48 teeth on the crank pulley (could go next door and look at one, but I'm too lazy! :) which would make the cam wheels have 96 teeth, so about 3.6 degrees per tooth, for an overall 11-12 degrees of play. It's rare to need to advance the inlet my more than about 8 degrees to improve midrange....

Of course I haven't had a look at how the adjustment was made, but if I was doing it, I'de just put the belt on 1 or 2 teeth out on the cam wheels, but then I am a but of "hatchet man".... LOL. This would throw the cam timing signal out by the same number of degrees, but if the cam signal is used anything like it is on Pectel (to determine whether No. 1 is rising during the compression or the exhaust stroke) then the absolute timing of the cam signal isn' important as long as it's within about 45 degrees of its design location.... in other words even a JECS shouldn't object to the cams being out a tooth or two.... all critical timing is derived from the crank signal....

Hope this helps,

Pat.

Dave
10th January 2001, 23:23
Thanks Pat , at last an answer that is usefull .
Cheers Dave

Firefox
10th January 2001, 23:42
Damn you Pat.. http://bbs.22b.com/ubb/wink.gif

But yes.. just move the gear a tooth or 3.. http://bbs.22b.com/ubb/biggrin.gif

J.

MorayMackenzie
11th January 2001, 01:39
If you are doing this to your engine, take advantage of the oportunity and inspect your cambelt, pulleys and tensioning system thoroughly... The last thing you want is a cambelt failure.

Richard.D
11th January 2001, 07:11
A lame, dangerous question http://bbs.22b.com/ubb/smile.gif - you can do this to a stock EU turbo too? Pat, not J!

Since fitting a PPP to a my00 I'm amazed at how strongly it pulls past 6.5k rpm.....I rarely go above 6. Would love to transfer some of this to mid-range...... http://bbs.22b.com/ubb/biggrin.gif

He, he, he....imagine the damage that could be done......

Thanks
Richard

pat
11th January 2001, 17:32
Richard,

J is a bit terse with his answers but there are very few things he hasn't dabbled with on Imprezas... :)

With regard to using GpN cam timing on a stock EU car, yes it is possible, BUT proceed with caution. The volumetric efficiency profile will be affected by the cam change, and although the Hitachi should compensate by virtue of the fact that it's measuring mass air flow as well as manifold pressure it may be a bit lean in the lower RPM band initially. After a while it should "learn" about the new parameters and will adjust accordingly...

You'll gain more midrange punch but you will lose a bit of top end power. Oh, fuel economy will suffer as well... just thought I'de mention that in passing :)

Cheers,

Pat.

Anders
11th January 2001, 17:39
Sorry it has taken so long to answer! I am glad the techies were able to give you sensible answers http://bbs.22b.com/ubb/cool.gif

On the road the car pulls instantly from low revs i.e. from arround 2000 it certainly runs out of steam by 6500.

(note I am not using water-injection http://bbs.22b.com/ubb/wink.gif )

BRDevelopments have decided that phase 5 engine rebuild will have a few new "trick bits" to compensate for the loss of top end http://bbs.22b.com/ubb/biggrin.gif

http://bbs.22b.com/ubb/cool.gif

Richard.D
11th January 2001, 19:40
Thanks Pat - sounds like I should be waiting 'til I've done the downpipe....and fitted a knocklink http://bbs.22b.com/ubb/smile.gif

Has anyone done this on an Impreza with the standard ECU (Euro, STi, 22b)? I'd like to have some idea of the real world pros & cons - and I'd love to see a dyno plot.

And how many with an aftermarket ECU have tried or used it (apart from the rally cars)? J, Pat, Moray & Anders only?!

Firefox - I *was* joking, honest!!

Thanks again, very interesting thread.
Richard

pat
11th January 2001, 20:48
Richard,

the more things you have in the car to monitor what is going on, the better. At least if you know something isn't quite right, you have a chance to back off until it's sorted....

I don't know of anyone running GpN timing on a standard car. Anders is (was?) running a JECS ECU and GpN timing, so we can conclude that this much works, but trying to find an original part in Anders' engine bay is a tall challenge :)

Also, note that the downpipe will increase volumetric efficiency by reducing back pressure so any ECU that only uses intake pressure will run lean as a result. The JECS should self-adjust to an extent due to the higher mass air flow on the intake side....

Don't think that Moray has tried GpN timing, or maybe only very briefly, think J is still running normal timing. I was going to try GpN timing when replacing the cam belt after swapping the crank sprocket for one with reluctor pattern compatible with the Pectel ECU, but that and a few other things were skipped due to time constraints. I'm still trying to figure it out, but my next engine may well be running variable valve timing, the Pectel can control this so it'de be rude not to! :)

Hope this helps,

Pat.

MorayMackenzie
12th January 2001, 01:56
Pat's right, I haven't yet tried Group N timing. I did look at this option before now, but I didn't want to loose quite as much fuel economy as this could loose you.

Anders
16th January 2001, 00:19
Fuel economy/17K rebuild...........

Group N was cool but I dropped to 120-140 miles per 60L fuel http://bbs.22b.com/ubb/eek.gif

Dave
16th January 2001, 09:39
Christ the fuel consumption in bad enough(I know you can't have power with out the fuel) but , to drop that much is no good to me . I'll keep the standard settings until I get a job with better pay http://bbs.22b.com/ubb/wink.gif .
Thanks to all who have answered Dave

Firefox
16th January 2001, 11:12
What Anders had done was a very crude way of obtaining more midrange.. nothing with tweaked (which would have increased economy and power). The process/trick is used by really teams, which are prevented from doing obvious mods. http://bbs.22b.com/ubb/frown.gif

Another down side are emissions.. they kinda take a hit with just moving the cams... not ideal.

J.

Richard.D
16th January 2001, 12:46
Hi Jay

So when we expect a Firefox Technologies Scooby cam profile then? http://bbs.22b.com/ubb/smile.gif

Cheers
Richard

Firefox
16th January 2001, 13:04
Cam profiles are being developed at the moment...

Based on UK and Jap spec engines... either utilising origianl cams.. or new items.

Shouldnt be long know. http://bbs.22b.com/ubb/wink.gif

J.

ps - And not just for the 2.0 engine http://bbs.22b.com/ubb/smile.gif

Anders
16th January 2001, 13:45
I should point out my horrendous fuel consumption was with the standard ECU/Group N cam timing. I hope with the BRD link in that the fuel consumption will be more reasonable http://bbs.22b.com/ubb/biggrin.gif