Boost 'struggle'??
 

I had a quick look to see if this has been asked before...and before i ask,

93 TT, 105,000km, 6spd, only mods worth mentioning that i know of.. is exhaust.

My question is: When i put the foot down in 2nd gear, i get a nice pull from the turbo from about 3800k upwards, but when i change to 3rd, it pulls a little, then makes a noise like its struggling? Instead of the nice boost that you'd expect, it just feels like shit to be honest. feels like its trying to boost but just can't.. It might boost for 1 sec or so, and then the power just turns off until i change gear...

I guess my question is, are you meant to get the same boost feeling in 3rd/4th gear as you do in 2nd? It does not feel or sound healthy. Drives perfect apart from this problem. Diagnostic is all clear. Cheers for any ideas!!

http://img40.imageshack.us/img40/9348/2222wt.jpg
By phuzion123 at 2011-09-01

http://img204.imageshack.us/img204/469/1111vb.jpg
By phuzion123 at 2011-09-01

http://img13.imageshack.us/img13/4732/021pzc.jpg
By phuzion123 at 2011-09-01

Through all gears you should still get a good pull as the turbos spool and as you move through your power band. As with any set up, as you move up through the gears it may be a little less. But from second to third as far as how hard it pulls shouldnt be that big of a difference that you would be concerned about. What kind of noise are you hearing and where does it sound like its coming from?

There's more load on the engine in higher gears, which means you're asking the turbos to work harder. 105K km is very low for a '93...are you sure that's the correct mileage on the engine and especially the turbos?

Also, maybe a dumb question but by any chance does the rpm needle go up without speed increasing?

If you could post a youtube vid with sound, that would be great. Hopefully it doesn't sound like this:
http://www.mkiv.com/techarticles/dea...eath_whine.wav

You know what, i think when this happens the RPM needle might keep going up without speed increasing, or very little speed increase. Is that bad??, ill check that out. Nah it doesnt sound like that one... The best word to describe the noise is kind of a stutter? maybe sounds a tiny bit like that clip but it's not a loud noise. Yeah 105,000 km is correct as far as i know. Car was imported from Japan 4 years ago at 81,000. I have the paperwork to prove that, and it's had 1 owner here in South Australia since then. ODO says 105 too. Owned by a female uni student so wasn't driven a lot.

Ill go for a quick spin tonight and check it out. The supra is off road at the moment because one of the rear wheel bearings has gone so im trying not to drive it too much till next week when it's fixed.

One other thing that may be of interest, It only seems to do it if i put the foot down in 2nd, keep foot down till 6.5k revs or higher then change to 3rd and put foot back flat. If i gun it in 2nd, change at about 5.5k then flat in 3rd it seems to pull nicely. Is it possible for the turbos to not be able to spool fast enough with the gear change and just fail?

Ill try to set my iPhone to record and then go through the gears, It doesnt do it every time, just sometimes.

Thanks for ur help.

Please let us know how the test run goes. If your rpm climbs without the speed increasing, it could be a slipping clutch. This problem gets worse in higher gears - try a high-boost acceleration in high gear on the highway.

Thanks for the info. Supra is off the road at the moment while i get this wheel bearing sorted. I'll do a test run as soon as its done.

How much PSI does a stock 94' run? I have no idea if the previous owner of my car changed it at all, but when i go flat out my boost gauge shows about 12 i think.. If i did run higher psi, what's the highest that you'd want to go?

11.5psi is the oem boost spec.

If you raise your boost, it depends on the octane of fuel that you run. With an otherwise-bone-stock* 2jz-gte, running 93 octane gasoline (calculated via (R+M)/2) you should never exceed 16psi. If you do so, your engine will be damaged in direct proportion to the amount you exceed this limit. For example, at 17-19psi, your 2jz-gte may survive for several years, but your compression numbers (and horsepower) will decrease gradually. Regularly hitting 20psi and above on 93 octane fuel, your 2jz-gte will likely die within months or even weeks. Keep it at 14 or 15 psi and your 2jz-gte should last just fine. When you want to 'play hard', fill the tank (don't mix) with 100+ motor octane unleaded race fuel, and feel free to boost to about 21 psi safely (ideally you'd monitor the oem knock sensors to find the exact limit).
Disclaimer1: all this assumes proper maintenance (eg. keeping your fuel filter changed, your cooling system regularly flushed, regular synthetic oil changes, etc., etc.).
Disclaimer2: Temperature and atmospheric density are also factors. High boost on very hot days is more likely to produce detonation. Near sea level the atmosphere is more dense, so cylinder pressures may be higher...which may be more likely to promote detonation, everything else being equal.

*When I say otherwise-bone-stock, I'm primarily referring to the timing and fuel curves in the oem ecu. In general, I mean no modifications other than those specified by "BPU" (with as many plusses "+" as you want that do not affect the oem fuel and timing curves). Anything that affects these curves (eg. a 'piggyback' ecu (eg. PHR MAP ECU II) or 'standalone' ecu (eg. AEM)), your max boost with any specific octane of fuel will depend on the (extensive) tuning required to properly configure these devices.

Oh nice... I run it on 98 octane every tank. So basically what your saying is, i could run my supra at 14 or 15 psi, (on 98 octane) and it should be fine?

How do i change the PSI? Boost controller install? (real newbie)

EDIT: My boost gauge looks like this
http://img40.imageshack.us/img40/1986/001cbc.jpg
By phuzion123 at 2011-09-06

- Am i right to say that if when i gun it, and the boost gauge shoots upto 1.0 that i am running around 14 psi?

Thanks

Is that 98 *motor* octane, or 98 *research* octane?

To raise boost, install a boost controller OR do one of the simple mods on mkiv.com
http://www.mkiv.com/techarticles/clamp_mod/_clamp.jpg

1 bar is about 14.503773800721814 PSI

just 98 Octane BP unleaded