YellowEvo03

iTrader: (1)

What are the most important differences in the performance/reliability of these two types of exhaust manifolds. It seems like Mandrel bent manifolds really drive up the cost of turbo kits, but they can't truly be worth the price difference. What are your guys experience/thoughts on this?

Buschur GT35R kit $3,000 with cast manifold
Other shops kits with mandrel bent manifold $4,500

honda-guy

iTrader: (55)

Cast mani tend to be more reliable and less prone to cracking. It’s cheaper to manufacture after the initial molding cost. More compact design but less flow and in most case does not have a good merge collector. It’s heavier than tubular mani and also absorb more exhaust heat which is not good.

Equal length tubular mani can be as reliable as cast mani if the right materials are used and designed well. they are lighter and usually have a good merge collector to direct exhaust into the turbine housing. the thinner wall will also absorb less heat from the exhaust. it can also be manufacture to the customers specs and because most are hand built and takes longer to manufacture that's why they tend to cost more than the cast (except for the cheap ebay ones). tubular mani has more advantage over the cast mani and that's why you wont see too many cast mani on a purpose built race car.

Juiced

Another benefit of a Tubular manifold if header length, it is very dificult to make an equal lenght cast manifold. Usually longer runner tend to increase tq and hold power longer as they can scavenge more effectively.

Flow is not as big an issue if the cast manifold was designed properly.

Gruppe-S

iTrader: (206)

Cast manifolds are cheaper to mass produce so 99% of the OEM manufactuers use this method. Also, cast manifolds are usually more duarble then tubular. The advantage of a tubular is its equal length design which in turn create more power in the upper RPM range. If you were to buy a tubular manifold, make sure they are well constructed with good weld and material. Most of the Ebay manifolds are made with very thin SS and will probably crack within a year.

An example of a good quality header would be Full-Race's 321ss. The material is thick and the weld penetrate on both sides. However, make sure you have the money to pay for it. A cheaper solution would be the Maxford manifold constructed with 3mm tubings. Also, we tested for 8 months with great abuse on and off the tracks without any sign of fatigue.

Thanks,
Tom

Gruppe-S

iTrader: (206)

Hey guys,

We just got in the Maxford header today:



-CNC billet flange
-3mm stainless steel tubings
-Tested on and off track for over 8 months

Thanks,
Tom

hondafan

iTrader: (25)

i like cast for daily drivers, had tubular on other cars and seemed to be welding cracks all the time. you can find nice S.S. cast manifolds that won't rust and cost less than half the price of a quality tubular and won't crack.

4-BNGR

iTrader: (3)

If it cracks, get it welded. That is all...