30 replies to this topic

[A9X]

Specifically speaking, who makes the best extractor/exhaust system for 5litres in the LX, and what combination?
Would the tried and true L34 system still be the best choice?

Welby

[micklx]

So does the merge collector join the 2 into 1 ?
Didn't the Race A9X's run a twin system?
Where is Gonzo Pipes located ?

[Struggler]

In my opinion,Gonzo pipes make the best pipes for motorsport.
1&5/8" x 14" stepped to 1&3/4"x20" into a merge collector 3.5" choked to 3" at the venturi. Fit an oval megaphone muffler with a reverse cone and that is about the ultimate set up.

Cheers Greg..

Personally I like a smaller collector choke, 2.5" or 2.75". This gets a bit more torque. Have to agree with everything else tho..........

[A9X]

Steal away Greg,

I'll get better info more input we get.

I'm specifically after torque in the low - mid rev range out of a 308.

Welby

BTW, whose/what are they ^ ?

Edited by A9X, 24 November 2006 - 05:35 PM.

[Struggler]

Exhaust is a peculiar thing, what works well on one motor may not work so well on another. It is however the one area where small changes can net large gains in torque and horsepower. I have spent a lot of money on computer programs and books and a lot of theory does not work in reality. Changing exhaust on the dyno is quick and easy and will usually point you in the right direction.

FWIW I have made the following observations, on engine dynos and cars running the quarter.......

I have never seen stepped 4:1 pipes produce more power than straight 4:1s,

Every time I have reduced collector size on 4:1 pipes the car has gone faster, quicker and made more peak horsepower, (much to the surprise of owners and dyno operators alike !!),

The tri-Y design is very efficient and can produce great power but exhaust manufacturers have got the sec. and collector ID sizes all wrong, to get them to work they need help,

The pipes that outright made the most power and torque on a VN headed stroker were homemade 1 7/8 primary tri Y's, on HQ headed engines the Pacemaker 1 3/4" tri Ys with larger sec. and collector pipes are gold,

My own SBC engine that pushes my HQ tonner to 11.0's only has 2 3/4" collectors,

Using too small a pipe is way better than using too large, by a long shot,

Collector size is crucial.

The best money I have spent on information came from this guy... https://www.headersbyed.com/ and I knew about him long before he got written up in Street Machine.

These are just my observations made over the last 15 odd years. If you want to talk specifics let me know, it all relates to CID and peak RPM.

Hope this helps.

[A9X]

That's gold Struggler.

My situation is a 308 , carb fed, that will be used for tarmac rallies.
Ideally, you want most torque/power low to midrange, for punching out of low speed corners and chicanes.
4 speed box at present , waiting on rule clarification before going 5 speed.
Diff ratio can be swapped to suit, probably 3.09/3.55.
Exhaust can exit before the rear wheels.

Welby

[Struggler]

That's gold Struggler.

My situation is a 308 , carb fed, that will be used for tarmac rallies.
Ideally, you want most torque/power low to midrange, for punching out of low speed corners and chicanes.
4 speed box at present , waiting on rule clarification before going 5 speed.
Diff ratio can be swapped to suit, probably 3.09/3.55.
Exhaust can exit before the rear wheels.

Welby

If its got HQ heads get the Pacemaker 1 3/4" tri Y pipes and be prepared to at least modify the collector. From the collectors merge the two pipes into a single after about 18-24" then maintain another 18-24" before a chambered muffler or dump pipe. The modified 1 3/4" tri Y pipes lose no torque to modified 1 5/8 tri Y so buy the big ones first.

Edited by Struggler, 25 November 2006 - 07:55 PM.

[Struggler]

What areas of concern are there with the pacemakers? Do you modify just the collectors or is there a problem with the secondaries sizing?

Changing the collector only shows the best gains for the least work. It is also easy to swap collector sizes on a dyno or track to get the best compromise for your combo. Changing the sec. sizes without testing can easily lead you up the wrong path !!!

Without going right into the maths, it all has to do with area ratios as the steps are made, ie to provide effective scavenging a reduction in area has to be made to ensure gas velocity is maintained, without becoming a restriction. This reduction ratio has to be tailored to the operating range of the motor. As an example, the total area of 4x 1 5/8 pipes compared to the total area of a 3" pipe is around 1.11. The same for a set of 4x 1 3/4 into a 3" collector is 1.40. This means the reduction and therefore scavenging capacity of the 1 3/4 - 3" pipes is greater than the 1 5/8 - 3" pipes. In practice I have found that 2.5" collectors on 4x1 5/8 pipes work really well (2-3 tenths faster over the 1/4). This should indicate the sort of ratio we are after. It should be noted that you can overdo the ratio and start to restrict the engine.

As another example the Pacemaker Tri -y that makes good power on VN heads has 1 3/4 primaries, 2" sec and 2 1/4 tertiary or collector size. Opening up the collector to 2.5" increases the power and torque. This set up is fairly fool proof and works well on all 355 type VN headed strokers. Now lets look at the HQ 1 3/4 primary tri Y's. The sec are 1 7/8 and the collector 2". The reduction ratios for these step downs are near 2. This works OK for a stocker but if you want to use the performance advantage a 1 3/4" primary offers you really need to open up the sec and collector size to get the ratio near 1.5. This lands fairly close to the VN pipe sizes of 2 and 2.5 ". I have seen cars use 1 3/4, 2 1/4 and 3" but they utilized convertors of over 6000 rpm stall.

This may all sound like a little too much but have a few reads of the info and do some math. There is no real magic in the right ratio, just different ratios for different applications. Like I said in the first paragraph, you really need to test to find the best setup for your engine and application, but what I have given you here will get you on the right track.

Hope no-one loses any sleep over this !!

Greg, as for the sand forming...... a friend of mines father is a real old school tuner, and has been for ever. He still hand builds open wheelers and such and I have seen him make some beautifully formed sand bent extractors. Real works of art with gentle curves to die for. They look great on the open wheel race rigs.

[ls2lxhatch]

Welby,

When I was looking for someone in WA to make extractors to suit an LS2 in a Torana the Butler's names kept coming up. Apparently they are brothers but two separate businesses.

Butler Built Performance Products
16 Cohn St
Carlisle 6101
Norm Butler � 9472 7373

Andy Butler
9361 0144
0439 995 123

I ended up purchasing extractors off the shelf from CAE because then custom made extractors we going to cost around $1700, there was a one month waiting list and they would need the car for a week. I intend to get my CAE extractors coated by this company once they have been test fitted.

Competition and Industrial coatings
Unit 1/8 Brant road
Kelmscott
(08) 9495 4237

[355LX]

As said above, Butler built (Norm) makes some awesome systems, from exhaust port to tail pipe. Have seen and heard only good reults from his workmanship.

Dave

[A9X]

Thanks all. that's a bucket load of info to keep me going for a few weeks.

Welby.

[A9X]

Thanks Poinsdexter,
I'll check the CAMS website as i have what i thought were the final rules following Targa West.

There is no mention of Modified Special as a category in my rules.

The rules we are building the car too at present don't allow us much modification at all, past the usual suspension/exhaust etc. Although we can have the exhaust exit before the rear wheels if clarance is an issue.

We must maintain carby feed, no EMS, no 9 inch etc. The major hiccups are the gearbox, my rules state 4 speed but otherwise free, and wheels size, my rules state 1 inch over diameter and 1 inch over width. So that gives me 15 x 7's to play with. Not a lot of variety in tyre choice.

Brakes are free but obviously are dictated by rim size.

Best i check out these rules you mention before going any further. I'll be pissed if they've changed them again. It'll be the 3rd version in 12 months.!

Thanks,

Welby

[A9X]

Poinsdexter i have had a look at the CAMS site, the tarmac rally rules are the same as given at Targa West 06 back in September.

These are the rules i am constructing the car to (C2).

I don't quite see where you are refering to Modern Special??

I do see that C3 allows five speeds however, and i am awaiting clarification from CAMS as to the reason for C3/C2 differences.

Welby

Edited by A9X, 27 November 2006 - 04:25 PM.

[355LX]

With the tarmac rally rules, is there a class you can enter that is open allowing any modifications to any vehicle?

Thanks,

Dave

[A9X]

in short , no.

In targa this year we had a number of cars 'by invitation"

A chev powered xjc jag and 2 commodores, 1 turbo powered. The organisors have told me that they allowed the jag entry bacause he had paid up well before CAMS imposed their new tarmac regs, and the commodore wasn't discovered to be that modified until pre event scrutineering, so they let him run under invitational.

The new tarmac rules have been accepted by the organisors because they see a greater benefit in having a possible 'circuit' between the other events like tassie and adelaide, than in bringing in highly modified cars.

There will not be an invitation category in this years targa west.

Welby