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The mkiv Supra Owners Club

Running Sweetly with Parallel Turbos


Nic

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The HKS dealer in HK has just opened a new workshop and fitted the first/only dyno here. I was having mis-fire problems after my engine rebuild so took my car along to get them to try to diagnose the problem. They ran my car on the dyno and found 2 problems, the first was that the wastegate actuator was not holding the boost over 1bar, the second was that the fuel regulator was shot and was causing the mixture to run lean.

 

I had a new stronger actuator, fuel regulator and a GReddy e-manage ECU fitted, the garage then suggested that I get the turbos set up in parallel. I went along with their advice and then watched as they ran my car on the dyno to set the timing and fuelling. It is well exciting watching your car on the rollers as they take it up through the gears until the rear wheels are going mental:eek::devil:

 

The moment of truth was test driving my car after they had finished setting it up. The first thing I noticed was the different exhaust note when I fired it up; I never use to think the exhaust was that loud before, but now it had a really deep rumbling noise to it at tickover and had a sinister growl when the throttle was blipped. Pulling away the car felt obviously different, rather than getting the initial pull and then the kick when the second turbo came in. Now the power delivery at low rpm was very smooth and strong until the engine hit about 3000rpm then all hell broke loose as both turbos spun up together up to 1.4bar. :)It felt good, very smooth and very powerful, then just as I thought my grin couldn't get any bigger I backed off and dropped down a gear 'bang....pop.....pop', came the appreciative sound from the exhaust on over run....:cool:

 

The garage gave me the dyno graphs of my car, the first was the initial run they did on the dyno and it showed the two peaks as each turbo came in in sequence and max'd at 340hp. The second graph was a power run after they had set up the turbos in parallel and mapped the timing/fueling, now the graph was one continuous smooth curve and reached a max of 429hp. Once I've scanned the graphs I'll post them so you can see what I mean.

 

I am really happy to finally get my car running well again after the last few months of tearing my hair out in frustration, big thanks to Phil and Chris for all their help in getting my car running sweetly again,

 

cheers guys

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The dyno run cost a few pennies but it was cerainly worth every one. I can not tell you how good it is to finally find a tuning place here that know their stuff, the only problem is it now opens up a whole new realm of tuning possibilities :flame Dev

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Is the car much slower below 3000rpm or is it not very noticeable?

 

It sounds like a similar power curve to my Mk3, which is ideal in my opinion. I didn't buy a MkIV cos I didn't like the sequential delivery, never thought of doing the true twin mod! :baa: :twak:

 

Never mind, I've just found out that my turbo is good for 1.6 bar - even BIGGER injectors on my shopping list I think!

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Doesn't feel any slower below 3K, it still accelarates well but it feels a lot smoother, e.g. at 0.3-4bar with both turbos in parallel the power feels similar to the single at 0.8bar but instead of getting a drop in boost as you do when the second turbo comes online on the sequential set up, you just get one huge surge from 3K+ which just seems to increase until 7K. I'll try and scan the graphs tomorrow so you can see the difference in the power curves.

 

I've also noticed that the rev limiter seems to come in slightly later now, I'm not sure if the limit has been adjusted when the e-manage ecu was mapped.

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Guest Martin F
Originally posted by randy

Nic,

 

Can you explain what you mean by "fuel regulator was shot and was causing the mixture to run lean" Are you talking of the Fuel Pressure Regulator? Was it faulty?:)

 

 

Are you taking the piss ?

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Randy, yes the problem I was having was with the fuel pressure regulator, it was faulty and causing the mixture to run lean. A new pressure regulator was fitted and this was set up to deliver a higher fuel pressure, the GReddy e-manage was then mapped on the dyno to control the fueling.

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This is the final power run on the dyno after the turbos were connected in parallel and the fuel/timing was set up. I'm no expert on dyno graphs so would appreciate any comments/opinions.

 

One question, is there anything I can do to keep the power climbing over 5000rpm or is this the limit of the stock turbos?

dyno.jpg

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wow that looks well smart for stock turbos,they are not hybrid stock turbos?

 

did you do a power run before the TTC conversion.would like to see what 1/4 times that will pull.i can see a flux of supra owners going for TTC mode.there is a lot of people in the states do it too.and my mate dunk has done it on his supra.was a bit of lag bottom end then it flys.but i am sure a hard launch of 3000rpm would help loads on an auto that is.

 

nic what other mods you done to your car.

 

 

well done

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Cheers Mark

 

No not hybrids, stock j-spec turbos, I thought the figure was pretty good too so questioned the garage about the hp units they used as thought it could be similar to the US dyno figures. From what I could gather the hp units are the same as they use in Japan which I believe are the same as used in the UK, can anyone confirm this?

 

You can see the full spec at member 177 on the registry, the only things missing are the GReddy ECU, new 2jzGTE short block and Chris W rebuilt head.

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Nic, we need a list of your mods to work out how best to get the figure to level off or rise after 5,000rpm...

 

Though my first thought would be a cam change. Probably 264's - though I don't think 272's will hurt you as you get so much power so early. Wilder the cam the higher the peak but the more you trade off your bottom end grunt.

 

Or just fit a staged shot of NOS! :D

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