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Discussion Starter #1
Hey guys,

I plan to go with a Precision 6466 or 6766 DBB turbo. Which T4 exhaust manifold should I be looking to purchase that is built for lapping days/time attack that is reliable, won't crack and performs very well??
 

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Discussion Starter #6
Budget for a good manifold would be around 1250usd and turbo will be divided.




Most quality manifolds aren't going to crack. I don't know the last time I heard someone says theirs actually cracked. Does the turbo have a divided exhaust turbine? What is your budget?
 

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My RPS cracked from the heat of HPDE. My Suprastore tubular manifold did not crack, great quality and can take the abuse. About $850? and is divided.
 

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Discussion Starter #8
My RPS cracked from the heat of HPDE. My Suprastore tubular manifold did not crack, great quality and can take the abuse. About $850? and is divided.

Do you have a link to the manifold you bought from Suprastore?
 

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For a dedicated road racing car/track day car I would personally stick to a SPA cast manifold.
 

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I was reading that log cast exhaust manifolds can have back pressure issues. What are your thoughts?
Not the ones he mentioned. The tubular will make more top end power, the log will shine down low. Both will last if you buy quality parts. It really depends on your budget and end goal.

Steve
 

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So far no issues with the 6466 and PHR Street Torque manifold. Boost hits real hard around 3800 RPM. Very fun on the street, have not tracked it. One full year of use. Made about 450 whp with the stock 550cc injectors
 

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So far no issues with the 6466 and PHR Street Torque manifold. Boost hits real hard around 3800 RPM. Very fun on the street, have not tracked it. One full year of use. Made about 450 whp with the stock 550cc injectors

Very nice! What boost? Any headwork?
 

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So far no issues with the 6466 and PHR Street Torque manifold. Boost hits real hard around 3800 RPM. Very fun on the street, have not tracked it. One full year of use. Made about 450 whp with the stock 550cc injectors
This is with no modification to the stock head. Boost varied between 17-19 PSI using an AEM TruBoost Controller, Stock ECU, and Fuel Cut Defender. Pretty simple setup. I'm in the process of going to an AEM Infinity and larger fuel system so I can get better logging and make a little more power. I've refreshed all the seals on the engine but still running stock internals.
 
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So far no issues with the 6466 and PHR Street Torque manifold. Boost hits real hard around 3800 RPM. Very fun on the street, have not tracked it. One full year of use. Made about 450 whp with the stock 550cc injectors
would definitely like to see a back to back with a 6466 and a 6870.
 

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For a dedicated road racing car/track day car I would personally stick to a SPA cast manifold.
Not the ones he mentioned. The tubular will make more top end power, the log will shine down low. Both will last if you buy quality parts. It really depends on your budget and end goal.

Steve
This is with no modification to the stock head. Boost varied between 17-19 PSI using an AEM TruBoost Controller, Stock ECU, and Fuel Cut Defender. Pretty simple setup. I'm in the process of going to an AEM Infinity and larger fuel system so I can get better logging and make a little more power. I've refreshed all the seals on the engine but still running stock internals.
There is nothing inherent in a cast manifold that gives it a better power curve. However, on a tubular manifold, like the ports in the head, the length and diameter of the tubing and design of the merge collector have to be appropriate for the engine speed and air flow. A [email protected] manifold is going to be really bad at 3000rpm. A manifold that is strong coming off the corners at 4000rpm probably won't have the legs of the [email protected] manifold. It is a matter of finding the right balance.

The second part, especially for road racing, is that the manifold is strong enough the support the mass on top of it being thrown hither and yon at 1.5G or more. NA manifolds don't have to deal with that.

That said, TTBOMK there is no Supra running a competitive road racing class where a few hp will make any difference. Can you really tell the difference of maybe 50hp from a cast manifold to a tubular one designed for the same power/rev range unless the car is on a dyno or another similar car is there fender to fender and 5ft down the straight makes a difference between passing or staying behind? Will the manifold really be the bigger improvement rather than fresh tires or a set of Penske shocks?

This is where some (with big budgets) go for custom headers: https://burnsstainless.com/ Some articles, and their spec form may be enlightening. Also, they can sell you the tubing to fabricate your own.

Full-Race lists different hp levels for their different manifolds, but any specs other than flange and WG. A look at the pictures clearly shows the difference between a T4 twin scroll IWG for 400-700hp and a T6 2 EWG for 1100+hp. https://www.full-race.com/product-category/toyota/2jz-gte-mkiv-supra-jza80/

Sidebar: if making your own, Burns SS sells the bent tubing and digital TIG pulse welders are available from Eastwood for $1100 (https://www.eastwood.com/tig-200-digital.html) and Everlast for $1650 (https://www.everlastgenerators.com/product/tig-stick/powertig-210-ext)
 
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