Need some professional advice on cams

[Trevor]

Originally Posted by TomsSVX

Yes, I would say they are getting more complicated because what I thought I knew of our previous cams is now proven incorrect. So all things said at this point you are suggestting using the exhaust cam profile and retarding the exhaist cam 1 tooth(7.2*) in order to raise the powerband? This would be an ideal setup for someone like me who is spiking off the rev limiter with 6 gears

Tom

No Tom I am not suggesting this as the best way to go. It would appear that you have not properly read the thread. I have published what I consider are the most logical inlet figures and you you should refer back for them in this thread and understand the thoughts behind them.

I now add figures which I consider best in respect of the exhaust cams. In all of this I understand that that you will have to compromise by using the nearest profile the cam grinder may have on hand. A few degrees either way should not be of concern, provided that alterations are applied with due consideration.

Exhaust Duration:- 267* or alternatively, 275* i.e. seat to seat.

Opening:- 75* BBDC or alternatively, 80*.

Closing:- 12* BTDC or alternatively, 15*.

You must accept that these figures are based on my estimate of your requirements and you must be the final judge. In this regard I do not regard the second set of figures included, as representing a wild cam grind. You have tried the very coservative approach and have made it clear that you wish to be a little more adventurous.

The induction control system should remain effective further up the rev range. However I would firmly suggest that a switch be placed in the induction control valve circuit, so that runs can be timed with the valve constantly open, as a simple worthwhile experiment.

FIxed short inlet tracts are after all in line with sporting requirements and the original system is fitted mainly for the benefit of the commuter driver. This is not rocket science and the principals will be well known to all and I hope our lecturer does not jump in and tell us all how to suck eggs! The flat more even power curve may pay dividends, even though on paper there is shown to be a small loss on the way up. I would accept repetitive runs at the strip, as being more reliable than dyno testing and a lot more fun and cost effective! Have some on me.

***** P.S. Tom you have said :- "Yes, I would say they are getting more complicated because what I thought I knew of our previous cams is now proven incorrect."

A problem remains in that we do not in fact know exactly what is incorrect. Harvey has selfishly not answered a simple yes or no, to my continuing question in this regard. Meantime we all remain in the dark. However I do agree that the specified duration, whichever way arranged, had little chance of providing any real kick in the butt.

[oab_au]

Originally Posted by TomsSVX

I have made my decision a while ago to go ahead and have my next set of cams drawn to the design of the exhaust profile. My only question I have been waiting for to be answered is, what should we do witht he exhaust cams, leave them be for a mild gain or should we be more focused on what we should do with them next. I apologize for my absence but I have merely been listening in and taking notes at this point.

Tom

Tom you would be wasting your time using that cam in your 6 speed car. You really need to be looking around the Stage 2 that I suggested. Around 15 to 20* extra duration and more lift.

These cams that Mychailo found look the goods.
http://www.subaru-svx.net/forum/show...32&postcount=5
8.75 mm lift on each, and around 200* duration. These are very close to the set that my Son used in his 3 Lt Datsun. Running these cams, with a 119* inlet LC, 114* exhaust LC, on a model, gave these figures.

RPM 3000 4000 5000 6000 7000
Kw 73 129 182 203 204
Nm 232 309 348 324 279

These would suit the 6 speed gear box that you have, and produce the level of performance you are looking for.

Harvey.

[dynomatt]

Second the comment that the exhaust profile isn't going to get you where you want to be.

Advertised of about 250 degrees would be nice which probably equates to close to 210-220 ish at 0.050".

Can the stock EFI system deal with that?

Matt

[TomsSVX]

the stock air metering system cannot but the fuel system can. By using my Stage2v5 ECUtune I can now reach appropriate power levels without losing my ability to accurately monitor airflow and temp.

Harvey, no offense but I would like to ask the others in this thread if these figures seem correct. I would also like the question the possibility of valve float at 8.75mm of lift with more duration. Don't forget it will be spinning at or around 7krpms

Tom

[dynomatt]

Valve float is very unlikely. Remember, that's traditionally been the domain of large single valves, rather than a multi-valve arrangement.

I don't subscribe to Harvey's 8.75mm of lift theory but then he hasn't replied to me why that is. I'm looking for a much more aggressive profile and will be aiming for about 10mm with probably about 270-280 advertised duration.

[TomsSVX]

From what I understand Subaru is well know for keeping their valve tensions low. I also believe we get coilbind at 9.5mm of lift I am looking for something to give me significant gains but still allow the car to be streetable. I am also not sure that higher lift will give us a better gain as you are implying

Tom

[dynomatt]

According to others, coil bind is correct at that lift. I'm proposing new springs.

Mine is not going to be streetable...in fact, quite the opposite.

From my perspective, you (and me when I get my car) will be going to lengths nobody else has gone to...does that mean we will have problems, absolutely...does that mean that anybody else knows what will happen, absolutely not.

I think you've reached the point where you're starting to get too much information. It's now up to you to make a decision and go with it.

You can be conservative with cam choice and not suffer...if you go too wild, you will suffer.

I think the 10mm is reasonable. I base this on my prior knowledge about the point where you get maximum flow, and also on the work done by VTSuby who claims max flow is at about 10.something mm lift.

Flow = HP, but it's up to the package of EVERYTHING to realise that. Just changing the cams to the spec that gets you the most flow, will not realise the gain. It will come with ECU changes, compression, headers, intake changes etc. Then, and only then, will max power be achieved.

You' re after a streetable package. What one person defines as streetable is very different to anothers. Will your proposed cam be streetable absolutely. Will mine...they might be (by streetable I mean that mine would only make power from 5000rpm up!!).

At the end of the day, you're on the edge...make an educated decision, and live with the consequences.

Either way, I firmly believe there is more to be gained, and you sound like you're in the best position to test that.

As I've said before, I'd be interested to find more about the WRX that had a claimed 212hp ATW. Lots of factors can affect that outcome, but frankly I think it's worth exploring, because what it says to me is that with just a simple change to an aftermarket programmable ECU, 20-40hp can be found. That's cheaper than cams.

Matt

[TomsSVX]

Thanks for your help guys, I am now on the fence about a lot of things I will see how it goes in the next couple weeks

Tom

[Trevor]

Interesting that none have the balls to back their hot air with exact figures. Not even within + or - 7.2*.

[dynomatt]

Trevor,

You'd be aware that I don't own one of these yet. You'd be also aware that I have some knowledge, and am not just another punter.

I'm prepared to stake my claim on the combination of my knowledge (gained from past experience) and the commitment to try it out once I get a car.

Until then, I agree, it's potentially hot air but it's certainly more educated than some.

Matt

[oab_au]

Originally Posted by dynomatt

Valve float is very unlikely. Remember, that's traditionally been the domain of large single valves, rather than a multi-valve arrangement.

I don't subscribe to Harvey's 8.75mm of lift theory but then he hasn't replied to me why that is. I'm looking for a much more aggressive profile and will be aiming for about 10mm with probably about 270-280 advertised duration.

Sorry Matt if I missed the question.
If you want to give me the Lobe center settings that you would like the 10mm lift, 275* cams run at, I'll give you an idea what the results would be.

Harvey.

[Trevor]

Originally Posted by dynomatt

Trevor,

You'd be aware that I don't own one of these yet. You'd be also aware that I have some knowledge, and am not just another punter.

I'm prepared to stake my claim on the combination of my knowledge (gained from past experience) and the commitment to try it out once I get a car.

Until then, I agree, it's potentially hot air but it's certainly more educated than some.

Matt

I agree Matt and I hope I may have provoked you towards submitting figures which have been applied to the rally cars you mention as having workrd on.

The debate had the potential to contain real content, but this has sadly been missing. There will surely be many interested in this subject provided facts are included. To date there has been little submitted in the way of honest fact.

[Trevor]

Originally Posted by oab_au

Sorry Matt if I missed the question.
If you want to give me the Lobe center settings that you would like the 10mm lift, 275* cams run at, I'll give you an idea what the results would be.

Harvey.

Presuming that the question relates to the subject of this thread, I will state that a lift of 10mm i.e. an increase of 42% is not feasible on several grounds. An exact assessment of all the results i.e. exactly that which will occur in all respects, will be awaited with interest.

Harvey, we are still awaiting adivice on the lobe centre settings intended in respect of the modified cams specified by you, but paid for by others. This has become THE question.

[dynomatt]

Harvey are you using Engine Analyser Pro? If so, I'd be keen to get some of the engine detail that I'm missing from so that I can play too.

Lobe centres for this motor would probably be about 105-110 degrees.

Trevor...I'd like more info to backup why the 10mm lift I'm proposing "is not feasible on several grounds". I'm proposing 10mm as a good start given the valve sizes, and am well aware that the valve springs are a problem. I'm proposing a change to them and also may need to grind down the bucket retainers to clear the cam. But otherwise, I'm not sure why it's a problem?

I'm exploring whether I can get the compression ratio to about 12:1 too as I think that's where I want to aim for rally use.

Matt

[oab_au]

Originally Posted by dynomatt

Harvey are you using Engine Analyser Pro? If so, I'd be keen to get some of the engine detail that I'm missing from so that I can play too.

Lobe centres for this motor would probably be about 105-110 degrees.

Trevor...I'd like more info to backup why the 10mm lift I'm proposing "is not feasible on several grounds". I'm proposing 10mm as a good start given the valve sizes, and am well aware that the valve springs are a problem. I'm proposing a change to them and also may need to grind down the bucket retainers to clear the cam. But otherwise, I'm not sure why it's a problem?

I'm exploring whether I can get the compression ratio to about 12:1 too as I think that's where I want to aim for rally use.

Matt

I use a licenced one from Lotus Engineering. If you PM me with what you need, I'll give it to you.

Harvey.