only 10psi on a TD42

[Angus Burger]

Hi all I hope that you can help me out.

I have just finished fitting a TD05 16G ( out of an evo 7) to my TD42 safari. I made a j pipe using 50mm OD pipe so about 44mm ID. A full 3 inch exhaust with no mufflers. I have fitted a boost gauge and an exhaust temp gauge pre turbo. I have would the fuel screw in 1 turn. i get a max temp of 600C when working it hard up a hill etc.
It has made a big improvement to the way it drives.

PROBLEM with the wastegate wired shut i can only achieve 10psi of boost. i would like to run more like 15psi.

Do you have any suggestions about why its not making more boost?

Cheers Angus

I forgot to add that it doesnt spool up as quickly as i would have expected starts around 2000rpm and makes 10psi at around 3000rpm.

[tweake]

pre turbo temps a bit on the cool side. however max temp and max boost will depend a lot on which TD42 you have.

have a BIG read through http://www.patrol4x4.com/forum/nissan-p ... lts-57407/
not sure what they mod on the TD05's

[Angus Burger]

Thanks for your reply.
Its an 89 swb so the older silver top motor.
I read conflicting info on what sort of temps you can run.
In your opinion what is a safe pre turbo temp

[tweake]

700c should be ok with the older motors. just watch what your smoke is like in the low rpms as the turbo is probably fairly laggy with a J pipe. over fueling before the boost comes up can kill the engine. something the egt guage won't see.

it would be better to find what they change in the turbo and get a decent manifold. they are meant to go quite well just with stock pump.

[Angus Burger]

do you think that the only reason that i can only get 10psi is that i have a restrictive j pipe and not enough diesel.

I forgot to add the j pipe is made from 2 50mm od pipes not just 1

Cheers

[tweake]

sorry i didn't even think about the pipe sizes.
if you have the gear make a turbo drive gauge. ie a boost gauge with a coil of copper pipe connected to the pre turbo exhaust. give you an idea of exhaust back pressure and compare that to boost pressure.

[Crash bandicoot]

waste gate wired shut?


your using a turbo designed to feed a 2 litre engine 18 psi of pressure at 4000+rpm....on a 4.2 litre engine?

what does the TD42 red line at 4200???

sounds like you need to change the propeller on the exhaust side to create more resistance against the exhaust gas as it flows through the housing.

in effect you are using a turbo that is designed to start operating at the top of a TD42's limit.,

Not enough volume = not enough rotating speed = lack of pressure to drive the turbo.

you are asking the turbo to shift twice the air at the same rpm's to make it effective.

[tweake]

turbo is about right. turbo off a 2 litre petrol is about right for a 4.2 diesel. however it could do with better compressor. but then again better exhaust manifold would help as well.

[Crash bandicoot]

turbo is about right. turbo off a 2 litre petrol is about right for a 4.2 diesel. however it could do with better compressor. but then again better exhaust manifold would help as well.

more to it then that, if the gates wired shut that thing should be blowing the silicone joiners off and usual symptoms of boost spiking. even with a stock manifold.

RHF4 VF19 would probably be better for that then the 16G6 from the makinen and 7 evo

[crazyclark31]

what size 16g you using? For it to spool up early you need to be using the "small wheel" As the big wheel will be laggy.
Also having only one pipe from the mainfold to the turbo will help. Basically you want to get the exhaust gas traveling as fast as possible. This also help keep the gas flow temps up to get the turbine spinning.

The shorty i turbo'd with a j pipe had one 50mmod pipe from manifold and a wrx tdo5.(16g small wheel). Boostedfrom 1100rpm with max boost(15psi) reched at 2100rpm when nailing it.


is messy but worked really well. Used two steam bends welded into one for inital bend

[tweake]

turbo is about right. turbo off a 2 litre petrol is about right for a 4.2 diesel. however it could do with better compressor. but then again better exhaust manifold would help as well.

more to it then that, if the gates wired shut that thing should be blowing the silicone joiners off and usual symptoms of boost spiking. even with a stock manifold.

may not if its under fueled.

[slide]

Is wastegate definitly fully shut? If its just a crack open it'll lower boosting markedly.
Where is your boost guage plumbed into?
And any intercooler etc, or just hot pipe?

[crazyclark31]

also check the condition of the turbo itself. If its near buggered it wont boost up properly.

[DieselBoy]

You need to give it more fuel. Basically, the injector pump is only supplying just enough fuel to get you to 10psi with that turbo.

You need to modify the injector pump next.

You need to fit a boost compensator aneroid so it gives it the required amount of fuel to reach the boost you want, with out pumping out clouds of smoke and heating everything up off boost . It might even need a bigger plunger to deliver enough fuel to get that turbo working!!

[strx7]

needs more fuel, I have a similar sized turbo (VF36) on my cruiser and its fine. But when i was playing around with things i managed to restrict air going to the boost compensator on the injector pump, and i could only get about 3.5psi due to the lack of fuel going in.

[Chewy69a]

I have a TD05 16g off an evo 4 (basically the same as evo 7 but evo 7 has the titanium compressor wheel I understand)

Anyway I am getting 18 pounds of boost and can get around 700c if I labour it big time when towing. The fuel pump is stock but I did have to wind the fuel screw up as when I first got the turbo on and running it would only boost about 8 or 9psi.

I've done about 50,000km like this and did alot of towing the stockcar about so if it was going to blow then it would have by now.

I found a snorkel dropped my exhaust temps by about 50 degrees.

[Angus Burger]

Hi thanks for all your replies.

What do you guys thinks a safe pre turbo EGT is on a silver top TD42. I thought that 700c was too hot.

So if i summarise the turbo is a little bit too big for this motor (as i havent done any pump mods etc)


I have since added more fuel, another 1/4 turn on top of the original turn it feels faster ( that could be because i have disconnected the boat) but if i cane it i can get the EGT to hit 700c. It doesnt appear to make significantly more boost, maybe one 1 psi extra.

I read that you can divert all the exhaust gas into one side of the twin scroll turbine housing to effectivley 1/2 the .AR of the turbo.
Have any of you done this?
I am planning to do that tomorrow any see what difference it makes.

Cheers Angus

[tweake]

its starting to sound like you got the big wheel version.
have a look at the numbers on the turbo, someone should be able to ID the turbo exactly.
what effect the exhaust pipes have on it i don't know. there is a reason turbos are mounted as close as possible to exhaust side of the head.

[crazyclark31]

the twin pipes to the turbo will slow the exhaust gases down which cause them to run out grunt when they get to the turbine.this is caused by the gases being able to expand which causes them to cool. this would stop the turbo from spooling up enough to make decent boost levels.

have read on other forums that the twin scroll turbos don't work on older diesels for that reason

[tweake]

have read on other forums that the twin scroll turbos don't work on older diesels for that reason

twin scrolls where originally designed for big old diesels.
there is just no gain with out the proper manifold and less of an effect with short engines and small turbos.

[Angus Burger]

S

the twin pipes to the turbo will slow the exhaust gases down which cause them to run out grunt when they get to the turbine.this is caused by the gases being able to expand which causes them to cool. this would stop the turbo from spooling up enough to make decent boost levels.

So are you saying that if i reduced them from 2 down to 1 it would speed up the exhaust gas and reduce the cooling affect( i have heat wrapped the two pipes already) and therefore increase boost pressure

[coxsy]

your engine will live longer if you keep pressure to under 15lbs

[crazyclark31]

a pic of your setup would go along way to helping us help you .
Also if you look at the pic i posted up earlier. i was running 15psi easily and if blocked the wastegate off it would boost waaay over 20psi.

[crazyclark31]

have read on other forums that the twin scroll turbos don't work on older diesels for that reason

twin scrolls where originally designed for big old diesels.
there is just no gain with out the proper manifold and less of an effect with short engines and small turbos.

Your right with that.
Was refering to twinscroll petrol turbos.
Am sure there is something else wrong with his set up as i have never had problems getting higher boost than what hes getting with similar setups.
Am thinking hes got to bigger turbo and flow speed issues.

[tweake]

yeah much the same thoughts. boost should have gone up more with the fuel increase. unless theres something daft like a leak somewhere.

i don't think trying to run on just one scroll would be any good. the small and big version of those turbo's i think uses the same sized turbine anyway.

[motardbiker]

Stupid silly question here, but do you have another boost guage to check with? Just in case the one you are using is a dud? I run a Gizzmo boost controller (digital display etc) and a manual analogue guage, theres about 2 psi difference between the two. Thought I'd put it out there.

[Chewy69a]

Get rid of the wastegate altogether, make sure its welded shut as it must be leaking if its not boosting. I had an adjustable external wastegate on mine and it wouldn't hold more than 10psi even when it was fully cranked up.

Either that or your airfilter is blocked, try running no filter and taking it for a quick rip. My truck drops about 3psi when the filter is clogged and when I first put a new one in it is like a whole new truck. (also egt's start climbing when its blocked so I know when its time to replace it)

And then lastly if both of those things fail to work then its your manifold but I've seen some crude manifolds work with no problems...

As far as turbo sizing goes I've seen guys use those quite big DSR turbos and they had no problem with achieving big boost numbers but they were laggy as hell. I wouldn't go smaller than a TD05 or it will get too hot and run out of puff up top.