Thread: Td5 Exhaust Manifold..

Originally Posted by John_D2

Agreed. Compare the pics, the standard has horrible airflow from ports 1 & 5, the Allisport has visibly better airflow. Without even putting them on the dyno you could see that the exhaust will exit better.

Personally, if I were going to keep my D2 I’d put on an Allisport & do an exhaust upgrade. My D2 does have the corresponding Allisport intercooler and a finer filter air filter.

You miss my point John.
Look at the exit of 1&5 into the main branch on the Alisport.
That is bad.
Where you've gained at one point on the Alisport at the head you've lost at a critical point.
Log type manifolds are used on turbo diesels as it reduces lag.
I'm the first to try and improve the comprises of OE designs but I think in this instance the factory has compromised head exit to get a more uniform flow into the turbine as that is the most critical point.
That's why I said I'd like to see a dyno result before passing judgement.

I've worked with brilliant head porters, the best in the country at the time.
I've made headers, merge collectors, spent hours on the dyno playing with this stuff several lifetimes ago, although admittedly never with turbo's.

For the $ spent I think there is better value elsewhere, e.g.putting that money into a hybrid turbo, especially if the stock manifold has been modified to overcome the warping issues.

Rick, are you talking about the bends that I’ve circled in red?

I am reminded of an article in an American hot rod magazine many years ago by David Vizard.
He tested a number of manifolds on Chev 350s including rams horns , logs and you beaut extractors both equal length and interference.
The result was that the most efficient was the Rams Horn manifold. For those unfamiliar a Rams Horn manifold is one that has the outlets rising up then down. Nobody would pick this as being the best flow manifold from its looks compared with the shiny and expensive extractors. But even the logs lost very little to the extractors.

The moral of the story is "Don't believe anything unless there are dyno records to back it up."
Where are the dyno records for the Allisport manifolds?

Regards PhilipA

Originally Posted by John_D2

Rick, are you talking about the bends that I’ve circled in red?

No, the point that they intersect with the others.
It's only a photo and may not be as bad as it looks, but it's a bloody acute angle.
I'd love to have one and try though!

As Phillip said it's not always intuitive until you've seen flow bench work done and seen what and why.

And I might be really wrong, but for the $$ I'd rather see back to back dyno results to prove it.
It's like back in the day at the track.
Seat of the pants might say, "yes, that's much faster" but with a lot of drivers it wasn't. The stop watch didn't lie.

Originally Posted by rick130

No, the point that they intersect with the others.
It's only a photo and may not be as bad as it looks, but it's a bloody acute angle.
I'd love to have one and try though!

As Phillip said it's not always intuitive until you've seen flow bench work done and seen what and why.

And I might be really wrong, but for the $$ I'd rather see back to back dyno results to prove it.
It's like back in the day at the track.
Seat of the pants might say, "yes, that's much faster" but with a lot of drivers it wasn't. The stop watch didn't lie.

It's also a matter of how the pulses from the exhaust interact when they reach the collector. The smoothest flow in the individual branches may not necessarily be the most effective at providing a steady stream of gases to the turbo.

Originally Posted by donh54

It's also a matter of how the pulses from the exhaust interact when they reach the collector. The smoothest flow in the individual branches may not necessarily be the most effective at providing a steady stream of gases to the turbo.

Absolutely.
Ultimately, equal length header pipes and a merge collector are ideal for maximum power, but may be laggy.
Split pulse pipes work well on a 4 cylinder to reduce lag but this is a 5.
Fabricated systems last about 2 seconds on a hard working off road vehicle, then we have the packaging problem of getting a snake pit of pipes to fit inside the engine bay of a modern car.
A cast iron log manifold is the best and most cost effective compromise for life plus lag.

I'd want to see a dyno sheet before plonking down $1200+ for a manifold but who knows, the gains may be equivalent to a decent IC?

How much is a VNT + map?
Double that?

I'm guessing the gain in useable power and torque would be much much more than double the cost of the manifold.

It’s Chinese made and from reading the poor grammar in the advert Chinese seller too.
I removed my original cast exhaust, de webbed it, had the mating surface planed and then the whole thing ceramic coated. Used new studs and havn’t had an issue in over 5 years.

stay away from stainless steel for an exhaust manifold. it will crack.
Stainless doesn't like to be continually heated and cooled and will work-harden.
Mine repeatedly cracked at the head flange and then one day completely broke off at the turbo end.
It was a good quality unit but not meant for long term use, more for racing.
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