The good old days ?

Doesn't the sky look pretty tonight - go look

so long as there are no cloud tomorrow, I'll be a happy man

So- are there any better manifolds available? And does anyone have proof that they help the 2.5 GTA engine

So- are there any better manifolds available? And does anyone have proof that they help the 2.5 GTA engine

They help the Atmo and if they help the Atmo get rid of exhaust gases then sure as eggs is eggs they will help a car under boost as well; the primaries look bigger than the overall bore of the standard turbo manifold

I was Wondering, as I can't rememeb what they look like I now, would the standard atmo zorst manifolds be any better, they are cast they could be modified, opened, flowed; do they fit a a turbo head? I am sure Mr faulks will know hes probably been there seen it done it it was at all worthwhile

John the Manifolds are not cheap though and you need further piping to complete the turbo installtion and box/pipe to exit everything, as a one off it all adds up

si21

[mettersl]

I'm no expert but I think it's harder on a turbo, longer, bigger diameter exhaust manifolds pre turbo increase lag, so there is a trade off between lag and power that an atmo doesn't have. I think exhaust pulse management might be a factor if the branches aren't even
Same with the pressure and intercooler side too I would expect, and positioning of the waste gate and dump valve ( plus sizing) are all factors.
Would be fun to have a go, but I expect supercharging is probably much easier to engineer.

Anyone who knows care to comment? That porker manifold looked like there had been quite a bit of thought gone into it.

Lee

I'm no expert but I think it's harder on a turbo, longer, bigger diameter exhaust manifolds pre turbo increase lag, so there is a trade off between lag and power that an atmo doesn't have. I think exhaust pulse management might be a factor if the branches aren't even
Same with the pressure and intercooler side too I would expect, and positioning of the waste gate and dump valve ( plus sizing) are all factors.
Would be fun to have a go, but I expect supercharging is probably much easier to engineer.

Anyone who knows care to comment? That porker manifold looked like there had been quite a bit of thought gone into it.

Lee

I can see what your saying about pipe size causing lag, however, I see it this way by using bigger manifolds you improve the performance/response of the engine; if the engine picks up without the need of boost youve not lost performance at the bottom of the rev range and you get to the point that the turbo will pick up sooner eliminating the effect of lag. You then have the benefit of free flowing gases further up the range so better response through the whole range; from the bottom through to an increased capacity at the top end with a bigger turbo or more boost. Remember the exhaust manifold improves the efficiency in removing exhaust gases so the engine will now be moving more gas more quickly, is any performance actually lost? You have however increased efficiency so depending on tutbo choice the turbo should come on boost earlier and harder for longer

I guess like all things it all depends on mods being matched cafefully.

I am not sure the exhaust manifold is as critical on a turbo in comparison to a normally aspirated car, to get reasonable power hence the GTAs crap manifold. The 21 turbo has a 4 into 1 manifold, the two outside branches on the 4 pot being longer than the two centre branches. That said 300 plus bhp is being extracted from this manifold. The 2.5 v6 has 2 extra pots so should produce more pulses and exhaust gas; I therefore cant understand why smaller spec T3 used on the GTA is more laggy than the lager speck T3 fitted to 21 tutbo. It can only be one of two things, the greater distance to the turbo in the pipe work and the really crap manifold or the combination of both.

I dare say equal lenth primeries on the exhaust manifold will help flow but probably if your going for an ultimate spec engine but is not vital. Interestingly the atmo manifold does not really have a secondary pipe just a large collector where it immeadiately joins the exhaust system. I have always been of the belief that the longer the primary the more torque is produced. This is because of higher gas speed obtained...I rest my case.

Q the Eggspurts Firing squad at the ready

si21

[mettersl]

Si,
I agree on everything you say, the only concern I have is on turbos more power usually means more lag, even if max power and torque are increased. This is a double edged sword.
The state of the art now is multiple turbos, often different sizes so you compensate for the lag by having either lower inertia turbo's to spin up faster, or a lower inertia turbo to spin up first, but these all need more controls so are probably impractical for the enthusiast tuner.
For quarter mile times the design is straightforward, big pipes, smooth curves, big turbo, low back pressure after the turbo, probably quite a bit of lag too.
For road use, short or no lag as a goal brings in more complexity.
I am not arguing the current system is good, it isn't, but the replacement needs thought...as you know.
No one bitten yet?
Lee

Si,
I agree on everything you say, the only concern I have is on turbos more power usually means more lag, even if max power and torque are increased.

Only if you increase the size of the rotating parts in your turbo, or change something that affects the air flow. More boost equals less lag, so if you wind the boost up on most turbo cars it will reduce lag, it may have a more pronounced step as it comes on boost so the lag seems more pronounced but the time to get on boost will still be less.

Out of interest whats the diameter of the manifolds on an A610 as opposed to a GTA?

[mettersl]

I suspect they are the same, bigger downpipe post turbo...


Anyone able to confirm- Clee, David?

Lee

I suspect they are the same, bigger downpipe post turbo...


Anyone able to confirm- Clee, David?

Lee

i can hear DG franticly clicking trying to find some more theory on the net

Getting there but the proof is in the pudding..

WOW....where did you get that wall paper from

[mettersl]

Looking good, when will it be running?
Cheers
Lee

WOW Tony that looks a great build, very nicely done fella. Ditto on the wallpaper where did you get it from???