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The mkiv Supra Owners Club

V8 Twin Turbo Project


Ryan.G

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Make sure you check and smooth any sharp edges on the Ross piston crowns. A set I had for the mr2 years ago needed some work before fitting. May be better nowadays :)

 

Good point mr Greenside. Will get machine shop to look at it

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Only just spotted this project Ryan! Read from start to now....All of this going on between you being a major part in the 8 sec street drag Supra ;-)

 

So is this engine not a multi valve? if its a 16 valve V8 then it CAN be used in Pro mod and ALL the MSA Drag classes!!

 

Forget twin GT35R's...Twin T67's??

 

Keep up the great work matey (";) Subscribed.

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Well Finally got the car on the dyno tonight and although the engine etc was perfect im going to have to redesign the way im running the vnt turbos.

 

With VNT turbos you should not need the use of a wastegate as the turbo choice should be selected to match the engine size and power output based on its back pressure as with VNT's when the valves are closed although it causes the turbo to spin up quick it also has alot of back pressure causing the boost to be low. (same idea as a restrictor ring on a BPU) Then opening the vanes increases the efficiency of the turbo and pressure + Power...

 

Well the issue i have is that the boost pressure is that low that its not enough manifold pressure to fully up the valves and hence ruining the Volume efficiency of the engine as the valves are staying nearly closed. So im going to redesign the piping now so that the vane control is driven off the exhaust pressure as well as monitoring the exhaust pressure pre and post turbo.

 

Its all good stuff though but just takes time but at 0.4 it made 430ftlb at 4000 rpm and 366bhp at 6rpm but the top end is crap at the moment due to the vanes being pretty much closed :D

 

I might have to go bigger though still as where it spools up fully by 1900rpm the engine compressor surges badly :(

 

Awesome turbos either way. Will get there though and im confident to say no supra will have such a torque curve when its done

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All the fun of trying something completely new :) Power figures are looking very good though.

 

Do you have a dyno plot you can post at this stage? It'd be interesting to see how it's going even with the issues you've found.

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All the fun of trying something completely new :) Power figures are looking very good though.

 

Do you have a dyno plot you can post at this stage? It'd be interesting to see how it's going even with the issues you've found.

 

Actually just looked at the graph again and its only 0.3bar of boost see below.... Flywheel and torque, FLywheel and boost.

 

image

 

image

 

When the boost drops the vains open up and you can see the torque shoot up. Im going to manually open up the vain fully and see what boost it hits with the wastegate blocked off. If its still got too much back pressure and not making enough boost for over 450bhp im going to strap a set of Gt28RS turbos on there as these will just bolt on and do 400bhp each.

 

But im confident these Vnt's wont let me down :)

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Well certainly learn't alot about VNT's in the last week.

 

With VNT's you dont need to run a wastegate as the vane angle controls the turbine speed and hence boost pressure.... Closing the vanes increases turbine speed and opening reduces.

 

Now in order you set up VNT's properly you need to monitor exhaust manifold pressure to work out the exhaust pressure vs manifold pressure that works best and is most efficient. Closing the vanes creates alot of back pressure and too much back pressure kills an engines volume efficiency so with VNT's Big boost is not always the best.... I also took the time to monitor the exhaust pressure post turbo to see how much a restriction my quiet exhaust was.. It measured 0.5bar at 6k which is massive and as soon as im back from madrid i will be acting the flow issues in the exhaust system.

 

Whe running a VNT turbo you must ensure your ecu has a closed loop wastegate control system to keep the manifold pressure equal in all loads as different loads (gears) effect turbine speed masssively!

 

The car made today 499bhp and 565fltb at as Jamie said 0.9bar! Any more boost and the exhaust pressures were going abit high and killing the breathing of the engine as well increasing the chance of det. My next moves are Water Injection to keep the vanes abit cooler as well as aiming to get the exhaust back box pressure down to 0.2bar max!

 

To measure back pressure guys the best way is to use a brake line fitting welded onto the exhaust where you want to monitor and then running some copper pipe coiled up to a transducer like below

 

image

 

With these extras im hoping to get my target of 550bhp and 600ftlb

 

Attached is some data which others might find interesting

 

Dyno Graph showing Bhp and Torque

 

image

 

Dyno Graph showing Bhp vs Exhaust pressure post turbo

 

image

 

Log from ecu - shows the exhaust back pressure and how it relates to boost pressure and vane angle.

 

image

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