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turbos advice


phat supra
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Turbos in True Twin Mode will it gain any more bhp or will that stay the same what are the pros and cons

 

thanks lee

 

BHP should be roughly the same, although it should give you more mid range power, at the sacrifice of some low down power.

 

I'd personally not recommend it unless you have some way of mapping the fueling/timing to suit and get the best out of the parallel setup.

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You will gain no HP at all, you will lose low RPM HP, it's just about the most ridiculous mod the Yanks have come up with for the MKIV TT engine, and they have tried really hard.

 

Toyota went to huge trouble, development and expense to create an engine with superb low end torque and good top end power, and then people want to undo all that work to create a lag monster with flat spots and fuelling and timing issues.

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You will gain no HP at all, you will lose low RPM HP, it's just about the most ridiculous mod the Yanks have come up with for the MKIV TT engine, and they have tried really hard.

 

Toyota went to huge trouble, development and expense to create an engine with superb low end torque and good top end power, and then people want to undo all that work to create a lag monster with flat spots and fuelling and timing issues.

 

I don't quite agree :)

 

If mapped to suit the parallel turbos, you can gain quite a lot of mid range power, where the sequential turbos are running flat waiting for the second turbo to kick in. Yes you loose low down torque and need to stir the gear stick a bit to keep the rpm's up, but the power delivery is much more linear and the extra mid range I got from the parallel set up I prefered.

 

There are some dyno graphs here of a car that Ryan has just mapped with the turbos running in parallel, this looks very similar to my old dyno map. It would be interesting to overlay a graph from a similarly powered sequential setup.

 

http://www.mkivsupra.net/vbb/showthread.php?t=142230

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We keep saying that True Twin mode doesnt gain anymore power but those that have done this mod 'and' had it fully mapped have gained power.

 

look at Cheekymonkeys dyno for example. he did a back to back comparison and gained about 20bhp top end! Ryan stated that in true twin egt's were lower and the injector duty was much higher therefore true twin flows alot more air.

 

Maybe there are no real power gains with the standard ecu but when it is mapped by a decent mapper you can gain more power as cheekymonkey has shown. 425 bhp on standard tubbies in true twin sounds pretty damn good to me.

 

Also I appreciate what your saying Chris about leave it the way toyota intended but as soon as you become BPU and are running around 1.2 bar the car loses its drivability by having a very sudden busrt of power at transition. This is shocking on damp roads and i think this is why some poeple like the True twin mod on thier BPU cars. The car is more laggy but become much more drivable at higher boost settings and as several dynos show it also provides for more power from 3800rpm and up.

ttc vs sequential.jpg

ttc power.jpg

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the above increases i've talked about are a fair comparison of a mapped sequential against a mapped true twin and not only that but its exactly the same care on consecative runs.

 

cheekymonkeys mapped ttc gained almost 20bhp over his mapped sequential.

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You will gain no HP at all, you will lose low RPM HP, it's just about the most ridiculous mod the Yanks have come up with for the MKIV TT engine, and they have tried really hard.

 

Toyota went to huge trouble, development and expense to create an engine with superb low end torque and good top end power, and then people want to undo all that work to create a lag monster with flat spots and fuelling and timing issues.

 

Not doing any work on single turbo Supras now then Chris:p

Oh! an i totally disagree to;)

 

Edit, as i suppose i should explain,why i think this, one of the main reasons for the lower torque figures in TTC mode is due to the fact that if done properly you don't have two butterfly valves in the intake and exhaust strangling it;) even though the first turbo is running in sequential, there is also a certain amount of back pressure due to the butterfly's, which will have a positive impact on low end torque,

the reason i think this is because when i fitted the Apexi exhaust butterfly to quieten the exhaust, i noticed that when driving around town, low end pick up improved noticeably when the valve was nearly closed, thus providing lost back pressure, which is why I'm now working on a boost activated butterfly that opens as soon as positive boost is reached, so the best of both worlds;)

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I would say a tuned TTC car will have worse fuel consumption, if its generating that much more power in the midband then that means its using more fuel.

 

If you want an economical car buy a Prius ;)

 

I would say mine is better, as its off boost until you want it to be, unlike the std set up, and when mapped properly, it will still be running the same AFRs as the std set up has, ie 14.7 right up to about 6 PSI, if your careful with how you do it.

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I would say mine is better, as its off boost until you want it to be, unlike the std set up, and when mapped properly, it will still be running the same AFRs as the std set up has, ie 14.7 right up to about 6 PSI, if your careful with how you do it.

 

I think fuel economy off boost will be the same on both setups, so cruising etc shouldnt be affected as the turbos dont really come into play.

 

But looking at the post below comparing a mapped TTC against a stock sequential setup I would say from 3000rpm up at WOT the TTC would be using more fuel, it has to as there is more power.

 

http://www.mkivsupra.net/vbb/showpost.php?p=1836423&postcount=9

 

 

TBH I have no idea why people talk about economy and supras in the same sentence, its a 3ltr turbo charged car :blink:

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the reason i think this is because when i fitted the Apexi exhaust butterfly to quieten the exhaust, i noticed that when driving around town, low end pick up improved noticeably when the valve was nearly closed, thus providing lost back pressure, which is why I'm now working on a boost activated butterfly that opens as soon as positive boost is reached, so the best of both worlds;)

 

Going a bit off topic here for a moment.

 

Dick, it's interesting you mention that, I was looking at this aftermarket exhaust valve the other day, it restricts exhaust flow at low rpms, increasing back pressure/torque, then opening at higher rpms.

 

There are boost activate butterflies on the market designed to do this also.

 

http://img174.imageshack.us/img174/131/tcvrz0.jpg http://img526.imageshack.us/img526/1917/tcvalvelz9.jpg

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Wez, I'm only going on my fuel consumption on long journey's, and the difference between sequential and TTC, i used to get about 300mls per tank before i went TTC and get 320-340 with the same sort of driving:)

 

Nic, yes i know there are boost controlled valves out there, and that one looks good, but i enjoy experimenting and making things myself:) its cheaper to;)

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Its all down to personal preference really,i have always been used to single turbo cars and like the power delivery, and although the sequential system feels quick, to me it just felt like am under sized turbo to start with and then disappointing when the second joined in, at least with two running it feels like a proper turbo = small single:)which i couldn't afford to do.

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