How big exhaust?

[majti]

I currently run 2" streight pipe single on 6.2d, but will be going bigger. Is dual 3" to much? Should i go single 3"?

.majti

[Screwy]

6 cylender 4.2 litre diesel?

3 inch is the go. duels is too much.

If its a 6.2 V8 deisel you have then possibly duels but i would only think max 2.5 inch anyways....

Screwy

[PGS 4WD]

From a performance perspective, not noise, you can't have too big. Once the exhaust has past the extractors in an N/A engine or the turbo in turbo application then the basic idea is to get it out as quick as possible with minimal restriction. There is often tuning work required if an exhaust deviates a long way from stock, hence why exhaust shops tend to be conservative in pipe si ze as the can't adjust the tune to suit.

Joel

[BadMav]

From a performance perspective, not noise, you can't have too big. Once the exhaust has past the extractors in an N/A engine or the turbo in turbo application then the basic idea is to get it out as quick as possible with minimal restriction. There is often tuning work required if an exhaust deviates a long way from stock, hence why exhaust shops tend to be conservative in pipe si ze as the can't adjust the tune to suit.

Joel

You can't have too big? Sorry, you're wrong, I race a Super street Drag car with 4 into 1 race pipes which originally had 4 inch collectors each side. I picked up 3 tenths of a second by simply reducing this to dual 3 inch. Another racer picked up half a second running a full muffled system, he was actually trying to slow it down to stay running in SS. I see it time and time again, guys come out in their "sick" ss commodores, drop the pipes and run slower than if they left them on.

Basically by making the exhaust bigger you slow it (the exhaust gas) down. It's not size that makes horsepower, it's flow. Same goes for a turboed diesel, my last ride, a 75 series turbo 2h with 3 inch mandrel bent exhaust no muffler was slower and made boost later than my brother inlaw's identical 75 series turbo 2h, same kit, same tune, same size tyres (same colour, yellow )etc etc. Yet his has a 2 1/2 inch shop bent exhaust with straight through muffler and surprisly better economy. Go figure?

My maverick (tb42) has extractors into 2 1/4 inch mandrel bent system with a straight through muffler. It's not loud, it's got plenty of torque down low (even on gas) and revs nicely to 4500.

A 6.2 litre slow revving v8 diesel, I'd go single 3 inch or dual 2 inch absolute max.

Keep the dual 3 inch exhausts for high revving 550 plus HP V8 petrols.

[majti]

A 6.2 litre slow revving v8 diesel, I'd go single 3 inch or dual 2 inch absolute max

Ok, thx man...

.majti

[PGS 4WD]

From a performance perspective, not noise, you can't have too big. Once the exhaust has past the extractors in an N/A engine or the turbo in turbo application then the basic idea is to get it out as quick as possible with minimal restriction. There is often tuning work required if an exhaust deviates a long way from stock, hence why exhaust shops tend to be conservative in pipe si ze as the can't adjust the tune to suit.

Joel

You can't have too big? Sorry, you're wrong, I race a Super street Drag car with 4 into 1 race pipes which originally had 4 inch collectors each side. I picked up 3 tenths of a second by simply reducing this to dual 3 inch. Another racer picked up half a second running a full muffled system, he was actually trying to slow it down to stay running in SS. I see it time and time again, guys come out in their "sick" ss commodores, drop the pipes and run slower than if they left them on.

Basically by making the exhaust bigger you slow it (the exhaust gas) down. It's not size that makes horsepower, it's flow. Same goes for a turboed diesel, my last ride, a 75 series turbo 2h with 3 inch mandrel bent exhaust no muffler was slower and made boost later than my brother inlaw's identical 75 series turbo 2h, same kit, same tune, same size tyres (same colour, yellow )etc etc. Yet his has a 2 1/2 inch shop bent exhaust with straight through muffler and surprisly better economy. Go figure?

My maverick (tb42) has extractors into 2 1/4 inch mandrel bent system with a straight through muffler. It's not loud, it's got plenty of torque down low (even on gas) and revs nicely to 4500.

A 6.2 litre slow revving v8 diesel, I'd go single 3 inch or dual 2 inch absolute max.

Keep the dual 3 inch exhausts for high revving 550 plus HP V8 petrols.

I think if you read my post you will see I said

past the extractors

. The collector is an important part of the extractor as it is this point that effects the reversion pulse. It is common to neck the collector down to a smaller diameter than the pipe as this creates the reversion pulse that lowers the individual extractor pipe pressure and improves scavenging. The important distance on an extractor is from flange to collector.

I would suggest that without the appropriate tuning after any exhaust modification then the results will vary. I have seen many a car dynotuned pipes on to go to the track and race pipes off and go poorly. All our race cars are tuned in the same form they run, be that pipes of or on.

Joel

[tanz-e]

From a performance perspective, not noise, you can't have too big. Once the exhaust has past the extractors in an N/A engine or the turbo in turbo application then the basic idea is to get it out as quick as possible with minimal restriction. There is often tuning work required if an exhaust deviates a long way from stock, hence why exhaust shops tend to be conservative in pipe si ze as the can't adjust the tune to suit.

Joel

You can't have too big? Sorry, you're wrong, I race a Super street Drag car with 4 into 1 race pipes which originally had 4 inch collectors each side. I picked up 3 tenths of a second by simply reducing this to dual 3 inch. Another racer picked up half a second running a full muffled system, he was actually trying to slow it down to stay running in SS. I see it time and time again, guys come out in their "sick" ss commodores, drop the pipes and run slower than if they left them on.

Basically by making the exhaust bigger you slow it (the exhaust gas) down. It's not size that makes horsepower, it's flow. Same goes for a turboed diesel, my last ride, a 75 series turbo 2h with 3 inch mandrel bent exhaust no muffler was slower and made boost later than my brother inlaw's identical 75 series turbo 2h, same kit, same tune, same size tyres (same colour, yellow )etc etc. Yet his has a 2 1/2 inch shop bent exhaust with straight through muffler and surprisly better economy. Go figure?

My maverick (tb42) has extractors into 2 1/4 inch mandrel bent system with a straight through muffler. It's not loud, it's got plenty of torque down low (even on gas) and revs nicely to 4500.

A 6.2 litre slow revving v8 diesel, I'd go single 3 inch or dual 2 inch absolute max.

Keep the dual 3 inch exhausts for high revving 550 plus HP V8 petrols.

I think if you read my post you will see I said

past the extractors

. The collector is an important part of the extractor as it is this point that effects the reversion pulse. It is common to neck the collector down to a smaller diameter than the pipe as this creates the reversion pulse that lowers the individual extractor pipe pressure and improves scavenging. The important distance on an extractor is from flange to collector.

Joel

so 2.5, in a tb42 is great, so long as it doesnt start too close to the collector?

[BadMav]

From a performance perspective, not noise, you can't have too big. Once the exhaust has past the extractors in an N/A engine or the turbo in turbo application then the basic idea is to get it out as quick as possible with minimal restriction. There is often tuning work required if an exhaust deviates a long way from stock, hence why exhaust shops tend to be conservative in pipe si ze as the can't adjust the tune to suit.

Joel

You can't have too big? Sorry, you're wrong, I race a Super street Drag car with 4 into 1 race pipes which originally had 4 inch collectors each side. I picked up 3 tenths of a second by simply reducing this to dual 3 inch. Another racer picked up half a second running a full muffled system, he was actually trying to slow it down to stay running in SS. I see it time and time again, guys come out in their "sick" ss commodores, drop the pipes and run slower than if they left them on.

Basically by making the exhaust bigger you slow it (the exhaust gas) down. It's not size that makes horsepower, it's flow. Same goes for a turboed diesel, my last ride, a 75 series turbo 2h with 3 inch mandrel bent exhaust no muffler was slower and made boost later than my brother inlaw's identical 75 series turbo 2h, same kit, same tune, same size tyres (same colour, yellow )etc etc. Yet his has a 2 1/2 inch shop bent exhaust with straight through muffler and surprisly better economy. Go figure?

My maverick (tb42) has extractors into 2 1/4 inch mandrel bent system with a straight through muffler. It's not loud, it's got plenty of torque down low (even on gas) and revs nicely to 4500.

A 6.2 litre slow revving v8 diesel, I'd go single 3 inch or dual 2 inch absolute max.

Keep the dual 3 inch exhausts for high revving 550 plus HP V8 petrols.

I think if you read my post you will see I said

past the extractors

. The collector is an important part of the extractor as it is this point that effects the reversion pulse. It is common to neck the collector down to a smaller diameter than the pipe as this creates the reversion pulse that lowers the individual extractor pipe pressure and improves scavenging. The important distance on an extractor is from flange to collector.

Joel

The numbers don't lie mate.

You go put your 5 inch exhaust on your subaru show and us how it's done.

[PGS 4WD]

I ran a single 3 inch on my stock TB4.2 and lost 5 kw, then I tuned it and picked up 8 kw on the stock figure. This is why exhaust shops always suggest small exhaust, if you don't tune the engine to the exhaust then you are wasting your time.

All around the world people are fitting exhausts to go faster on the quarter mile. It's all in the header pipes to the collector, length and size, but honestly I've only got 17 years experience running a chassis dyno.

Joel

[BadMav]

Seems like an an expensive way to gain 8kw. What did you change in your tune? Did you try tuning with a smaller exhaust?

[Guy]

Seems like an an expensive way to gain 8kw. What did you change in your tune? Did you try tuning with a smaller exhaust?

With allot of experience and a dyno on hand I doubt it.

[PGS 4WD]

That was one of my cheapest learing experiences, and the exhaust was fitted as I knew at some time I would turbo it. The vehicle was straight LPG with gasresearch and a delco 808 ecu running a 3D timing map. In regards to money spent in R&D on cars. In my own personal vehicles, not including customers I have;
332 stroker twin gasresearch HG wagon. Holley before the Gas.
400 CI B Block Mopar in Doge Phoenix, Holley and twin Gas research Carb.
VK 304 VN heads solid cam manual Duel fuel with delco and twin Gasresearch carby. 12.4 at 112 mph.
383 BB Mopar in Aust Charger, Twin Gasresearch Carbs. 12.9 @ 103 mph
200 rwkw GU diesel TD 42.
4.2 Turbo GQ swb 16 psi stock motor, single carb, twin converter.
Pulsar ET roller turbo Wolf v4x ecu
4.8L Patrol Haltech, extractors, single 3" exhaust 157 rwkW stock engine on 35 muddys.
5.7 Single TO4ZR 325 rwkW comp truck LS1 ECU tuned by me with EFI live.
XR6 Turbo, injectors, stage 2 process west intecooler, tuned with HP tuners.

And some lesser vehicles in between, all at some stage were daily drivers and I have used each vehicle as a development vehicle various things such as camshatft design, software practice, aftermarket ECU software and so on.

So as you can see its a lot more than a bit of dyno time and some 3" pipe.

Joel

[BadMav]

Righto mate, apologies for the previous post.

[ludacris]

That was one of my cheapest learing experiences, and the exhaust was fitted as I knew at some time I would turbo it. The vehicle was straight LPG with gasresearch and a delco 808 ecu running a 3D timing map. In regards to money spent in R&D on cars. In my own personal vehicles, not including customers I have;
332 stroker twin gasresearch HG wagon. Holley before the Gas.
400 CI B Block Mopar in Doge Phoenix, Holley and twin Gas research Carb.
VK 304 VN heads solid cam manual Duel fuel with delco and twin Gasresearch carby. 12.4 at 112 mph.
383 BB Mopar in Aust Charger, Twin Gasresearch Carbs. 12.9 @ 103 mph
200 rwkw GU diesel TD 42.
4.2 Turbo GQ swb 16 psi stock motor, single carb, twin converter.
Pulsar ET roller turbo Wolf v4x ecu
4.8L Patrol Haltech, extractors, single 3" exhaust 157 rwkW stock engine on 35 muddys.
5.7 Single TO4ZR 325 rwkW comp truck LS1 ECU tuned by me with EFI live.
XR6 Turbo, injectors, stage 2 process west intecooler, tuned with HP tuners.

And some lesser vehicles in between, all at some stage were daily drivers and I have used each vehicle as a development vehicle various things such as camshatft design, software practice, aftermarket ECU software and so on.

So as you can see its a lot more than a bit of dyno time and some 3" pipe.

Joel

You need any more mates Joel. (jokes) Very nice rides mate.

Cris

[cooki_monsta]

That was one of my cheapest learing experiences, and the exhaust was fitted as I knew at some time I would turbo it. The vehicle was straight LPG with gasresearch and a delco 808 ecu running a 3D timing map. In regards to money spent in R&D on cars. In my own personal vehicles, not including customers I have;
332 stroker twin gasresearch HG wagon. Holley before the Gas.
400 CI B Block Mopar in Doge Phoenix, Holley and twin Gas research Carb.
VK 304 VN heads solid cam manual Duel fuel with delco and twin Gasresearch carby. 12.4 at 112 mph.
383 BB Mopar in Aust Charger, Twin Gasresearch Carbs. 12.9 @ 103 mph
200 rwkw GU diesel TD 42.
4.2 Turbo GQ swb 16 psi stock motor, single carb, twin converter.
Pulsar ET roller turbo Wolf v4x ecu
4.8L Patrol Haltech, extractors, single 3" exhaust 157 rwkW stock engine on 35 muddys.
5.7 Single TO4ZR 325 rwkW comp truck LS1 ECU tuned by me with EFI live.
XR6 Turbo, injectors, stage 2 process west intecooler, tuned with HP tuners.

And some lesser vehicles in between, all at some stage were daily drivers and I have used each vehicle as a development vehicle various things such as camshatft design, software practice, aftermarket ECU software and so on.

So as you can see its a lot more than a bit of dyno time and some 3" pipe.

Joel

You need any more mates Joel. (jokes) Very nice rides mate.

Cris

playing the trump card i see joel!

[PBBIZ2]

Guys,
great read, so here is my question. I have 97 GQ 2.8TD LWB 110,000klm. Its pretty heavy with gear,and economy has droppedright dowm over the last 3 months. I am suspecting the injectors is part of the problem. The vehicleis stock engine wise, and I don't really want to do any major mods or try to scream the death out of it. It has a safari snorkle and Safari FM intercooler.
IThe exhaust is the factory stock 1 3/4" system and was thinking an upgrade might be worth it here as well.
Question then is, what do I do next?
1) Do I stay with the standard exhaust and just get the injectors replaced and tuned to optimum?
2) Do I upgrade the exhaust before doing the injectors, to something larger - currently there are 2 1/2 and 3" mandrel kits for this motor kicking around, then get the get the injectors changed and I guess the pump played with as well?

I am prepared to shell out the coin as its a vehicle that is well looked after, purchased new and I will probably never sell. I don't want to throw money away though if the gain is not going to be there.

Hope this is not too off topic - perhaps driven primarily by the exhaust dia question, but the other issues are related.
thanks
Phil

[PGS 4WD]

Has the economy dropped since adding all the gear?

An exhaust will certainly help, you can chip them too however they are not a strong engine or gearbox, so be warned!

Joel

[PBBIZ2]

Joel,

thanks for the comments. Its a GQ, so cannot be chipped. The econony has dropped over time, no doubt as the weight has increased. The motor is pretty poor from a torque perspective as you know. I have also installed a Marks reduction kit to the transfer kit and its made a hell of a difference in driveability off road.

Whats the recommendation then?
thanks