Torque dip fix?

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Black Light
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Torque dip fix?

Post by Black Light » 11/02/18 10:53

Just wondered if someone could tell me what they think is causing me a torque dip and how I might fix it?

Image
This is in WHP.

The engine is mostly stock, it has a nice intake, decat, back box and some lightweight parts with a link ecu.
Fensport did the main tune and this was just a quick run which made the dip better but it is still there and its a bit annoying as it hits on my day to day driving.

Thanks



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Re: Torque dip fix?

Post by MR2DI4 » 11/02/18 20:13

Is it a MK2 Turbo ? I presume so at 166.5Hp, which generation?

The TVIS is supposed to open at about 4200rpm but I wouldn't have thought it would have had that much effect if it was staying closed.

Overall thats pretty low Hp & torque for a Turbo. Maybe its the tune of the Link ECU but its quite a bit down on power compered to my stock ECU. Its quite handy to still own a stock ECU, they take about 5 minutes to swap over.

Depends on how much boost your developing as well.

Was that a 3rd gear run or do you have a speed delimiter which means you can do the test in 4th ?

My Gen 2 turbo is at a nice flat 170Ftlb and 225Hp at the wheels with the stock ECU and injectors at 15psi according to the Dyno but my gage is 17psi.

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Re: Torque dip fix?

Post by Black Light » 11/02/18 23:08

Sorry. Forgot to metion this is the BEAMS NA!
I need to check the map to double check the vvti.
The wheels are off an r32 gtr 16" so dont think those are the issue.
My only thoughts so far is that i have some weird restriction with a combination of my intake and exhaust?

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Re: Torque dip fix?

Post by MR2DI4 » 12/02/18 6:17

LOL well that does make sense, it somewhere between the older N/A and a stock turbo.

You would have to think mapping or else control of the variable valve timing.

Would rule out constants like the exhaust and intake.

Not sure that Toyota had the vvti fully sorted back then ? Subaru definitely have it sorted in 2004, it feels like you suddenly have a few psi boost in an N/A when it kicks in. You wouldn't expect a dip, you would expect the opposite, a sudden increase in Hp or at least a nice continuation of the curve.

Take a look at this.

http://www.adaptronic.com.au/forum/inde ... pic=4813.0

If I had to put money on it its tuning, however if you google "3sge beams dyno plot" you see a few with the same dip.

I would have expected a more "Peakier" curve that was assisted in getting that shape from the vvti

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Re: Torque dip fix?

Post by peteV6R5 » 12/02/18 9:24

never noticed it before,
just checked through quite a few of these (a few are beams as well)
https://www.google.co.uk/search?q=dyno+ ... 40&bih=769
pretty much all have a dip around the same 3500-4000rpm mark.
checked my dyno from when it was a 3sge and it had the same thing, not quite as pronounced and yes not beams.
I agree that it looks more like the setup on the link ecu that is giving a big variance in your power / torque lines
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Highland Drive 13/14/15/17/18
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Re: Torque dip fix?

Post by Black Light » 12/02/18 13:37

The vvti should definetly be working, i can tell the difference from the standard 3sge.

The vvti in my map comes in from 2500 before decreasing again after 4500 which i thought was fairly normal for this engine?

The map seems like the obvious culprit but when i was with it being mapped they said they could smooth it out but there will be less power - i.e reducing the power around the dip. But without spending more time on a dyno its difficult to say.

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Re: Torque dip fix?

Post by MR2DI4 » 12/02/18 20:35

I would be looking up the factory Hp for your exact engine.

The drive train losses are NOT 20% either, thats rubbish your looking at 6-8% unless your rear brake calipers are seized on.

Increasing the boost from 10psi to 15psi got 225Hp at the wheels so it negated the losses to give 225Hp at the wheels not at the flywheel.

Look up your spec, I suspect your current level of power is quite a bit down, that curve looks too flat to me for an N/A with vvt.

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Re: Torque dip fix?

Post by Black Light » 13/02/18 18:28

6-8%? I was under the impression that it was more like 15%?

Stock engine should be at 200ps (197hp) at 7000 rpm.

http://www.6gc.net/forums/index.php?showtopic=91467

Considering that my mods wont be adding much i dont think im far off depending on the drivetrain loss. This was also mapped safley and to 93 ron fuel to make it easy day to day reliable but i assume the stock is designed for 100ron?

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Re: Torque dip fix?

Post by MR2DI4 » 13/02/18 20:42

From memory my drivetrain losses were 5.6kW.

Pretty sure the Dyno had a motor that after the car was brought up to top speed, the operator depressed the clutch and the motor was essentially just driving the transmission. I guess the Dyno just measured the power required to the motor to keep the wheels spinning at the same speed.

It was shortly after the dyno run I also had problems with the rear brake calipers, a known problem with the MR2 so you want to make sure they are free from problems before a dyno run.

Think I read an article online somewhere about the Nissan GTR, it only had losses in the 10% region and that is a four wheel drive car. You only add 20% if you want to feel good about your Dyno result.

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Re: Torque dip fix?

Post by Black Light » 13/02/18 21:34

I think everyone likes to feel good about their dynos! Haha.
Okay so back to the torque dip everyone is pointing to the map/vvti?
If it turns out that this isnt the cause then do we have any other ideas?
I will also double check the calipers this week

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Re: Torque dip fix?

Post by MR2DI4 » 14/02/18 2:57

Just jack the car and spin the wheel, you should get several revolutions not one or even less.

The whole car should also easily just roll on the flat in neutral with the handbrake off if your lazy and don't want to jack it up.

How many miles has the car done ? a N/A is going to take a hit performance wise with high mileage, you really need to rebuild the head and clean up the valves. The intake valves in particular get in a real mess with carbon/oil build up and this really affects the top end power.

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