[roland2003]

Hi Guys, I said a while ago I would put up a thread on the turbo manifold design used in the GTT 300 Turbo conversion. This same level of design engineering has gone into every part of the conversion .
MATERIAL Our manifold uses 'Thick wall cold rolled seamless mild steel tube. This is the only material that is perfectly suited to the job. Despite this there are a number of Stainless Steel or thin walled manifolds out there (or worse still thin wall AND stainless). Stainless is just too britle for the job and risks fracturing,likewise thin wall tube may crack aswell. Mild steel turbo manifolds will not rust out either ,the temperatures are much too high for this to occur.
WELDING Not only do we TIG weld but we 'purge weld 'too.This involves a second bottle pumping argon inside the pipes. This is the only way to achieve full penetration of weld through the joints for maximum strength. Rarely used and skillful to do well.(so I wont be doing it!)
MANIFOLD DESIGN (PIPE ROUTING) The easy way is a log or box manifold, this can be either a single or double 'log' with 4 stubs into the log and one flange on the outlet to the turbo. This is much cheaper and easier to produce ,it also losses around 15% power compared to a proper 4 seperate branch manifold converging to '4 into 1' merge collector! - Our manifold is of the latter design .In effect the gasses from each cylinder are never 'fighting' each other; they join at the turbo entrance and not before.
MERGE COLLECTOR This part of our manifold is the transition from 4 pipes into one. All 4 pipes point directly at the turbine entrance, with no loss or change in diameter all the way from the ports .
PORT SHAPE Our manifold uses the first 40mm as a smooth and progressive transition from rectangular to circular. Round ports on a Mini manifold are a cheap easy but not very power friendly way to get the job done! The stock Mini ports are rectangular with R12 corner rads on the top corners and R6 rads on the bottom corners, its therefore important to match to this on the first part (entrance) of any exhaust manifold,
PIPE DIAMETER Our manifold runners maintain a carefully calculated cross sectional area. Too big or too small and youll lose power.
TURBO POSITIONING The manifold dictates where the turbo sits so is vital that the design has consideration to everything that connects to the turbo. If the turbo is too far back it will wack the bulkhead as the engine moves on its mountings. Too high and you either burn the paintwork or you are forced to use a very restrictive 90 degree turn on the compressor outlet. Design it for lhd cars , and you may have problems with the exhaust outlet elbow fouling the steering rack/column. Too far to the left (right if you put the turbo the other way round) and the compressor inlet diameter is either very small and/or you have to use a cone filter bolted directly on which pulls in hot air from the adjacent red hot manifold. We managed to use a 3 inch inlet all the way to the GTT top mounted airbox.Even with all this it must allow the fitting of good diameter oil return to the sump (gravity only, so no uphill runs) ,plus water in & out and oil feed.
BRACING How ever strong the manifold is you still need bracing. Why? Well without it although the manifold in itself might not sag at 1000 deg C , but the bolts holding it to the head may stretch. The manifold flange is only 50mm high and the top row of bolts is only 30mm above the bottom row, meaning the leverage pulls quite hard on these studs which are only in an alloy head. We use a strong stay bar mounted to the block which supports the weight and prevents twisting load.

ps If a manifold offering all this was available we would have used it, as it was a heck of a lot of work. As usual we ended up designing/making our own.
Best Regards Roland GTT

[roland2003]

Hi Guys, this manifold is also used on the forthcoming 280T qs.

[Shorty]

I think you may have persuaded me to ditch the idea of getting a GP next

[roland2003]

Hi Paul, although their are many routes to big power Minis. If your starting from scratch I think a bog standard facelift MCS with Chilli Pack (ie with LSD already fitted) then apply liberal coating of 280Tqs will be one of the best & most cost effective routes.

[Shorty]

Quote: Originally Posted by roland2003 (original)

Hi Paul, although their are many routes to big power Minis. If your starting from scratch I think a bog standard facelift MCS with Chilli Pack (ie with LSD already fitted) then apply liberal coating of 280Tqs will be one of the best & most cost effective routes.

I've already got the GTT220 Roland, and with new drive belt that you fitted last month

Could the modified JCW airbox be retained when moving up to 280?

[roland2003]

Hi Paul,no, but I had overlooked that not only can 'most' of the GTT Cold Ram kit be retained but also if you have(had) the GTT/JCW filter upgrade for the JCW cars ,all of that can be utilited, you do need the Rampipe and sleeve though that comes with the Cod Ram kit. In essence we will utilize what we can from both kits.

[MINI-Morgan]

Hi Roland,

Do you sell the manifold seperately? Very strange question I know......

[roland2003]

Hi Dave, no . TBH it is almost impossible to do a turbo conversion sucessfully DIY. It is very involved, requires a machine shop, welding shop and dozens of other parts to be designed &made as a one off. It would not be cost effective for you to do. I think to offer a manifold on its own for sale is misleading customers .
Also for most people the conversion needs to be an everyday driver... Cold start, sitting in traffic, cruise, MOT pass , road legal, no EML's, & no laggy monster that needs 3 seconds spool up time & min. 5000 revs.................to achieve all this is even more difficult. The 280Tqs will give people all of this and at a very competitive price.
Hold out for that Dave