Dump valve

[makeitfit]

I think a dump valve will help keep low revs torque up!
Is this true and if so who does one for the nissan turbo?
I'm trying to get more low down grunt, so looking to combine as many helps as poss.
eg intercooler fan and viscous fan off.
Any other ideas please?

 

[zippy656]

ooh let us know how you get on..


i keep loking at the intercooler fan, for when towing realy

 

[Terranosaurus]

Dump valves don't work on diesels.

Wastegate doesn't "dump" anything anywhere, it bypasses exhaust gasses around the turbo impeller in order to limit boost.

Dump valves are something completely different (and also totally pointless on diesels), they "dump" airflow to atmosphere (hence the pshhhh noise, though the better ones actually recirculate the air, but are virtually silent so boy racers don't like them) when the throttle is closed. On a petrol engine there is a physical throttle choke/flap that will stop the airflow, diesels don't have one. If the airflow is stopped the turbo will stall (ie stop) and when the throttle is reapplied there will be greater lag (ie takes longer to get boost back as the turbo spools up). On a diesel as there is no throttle choke the air just goes into the cylinde as usual, actually helping to maintain turbo turbine speed as the volume of exhaust gases stays high, whereas on a petrol the exhaust gas volume and speed drop off sharply.

As an aside a couple of seasons back M-Sport and Pro-drive on the Focus and Impreza respectively introduced a boost recovery system whereby, any excess pressure was diverted to a large storage tank (in the rear bumper on the focus IIRC), when needed this air could be used to supplement the turbo at times of low boost hence helping to reduce the lag effect.

 

[lacroupade]

and TBH Pete, not sure removing the 'vicious' fan will do much for your cooling.

Intercooler fan might help a bit though, but not sure any difference would be really worth the effort/expense. If you want to improve i/c performance at low speed, i.e. not much wind rushing through the scoop, I'd have thought water spray with a bit of alcohol a better bet....have seen them used on scoobies but reservoir doesn't last very long...

Trouble with i/c fan is I think you might fairly quickly reach a point where it starts to impede airflow rather than help it but the only way to know is some accurate temperature measurements along the way....

frankly you'd be just as well off getting a chip for the expense and effort you'd have to otherwise put in wouldn't you? And one for the truck while you're at it....:augie

 

[zippy656]

davemud has teh i/c fan on his. ask him.

 

[extreme-4x4]

we've been through all this before... think toolbox suggested fitting a turbo boost gauge and tweak the turbo slightly.... even if you don't tweak a boost gauge will be a handy tool , as would a few other gauges.
battery. oil pressure etc

 

[extreme-4x4]

the other route was the 200sx turbo and something else... who had a price for that,,, it was 400 quid or so wasn't it

 

[Darwin]

I think a dump valve will help keep low revs torque up!
Is this true and if so who does one for the nissan turbo?
I'm trying to get more low down grunt, so looking to combine as many helps as poss.
eg intercooler fan and viscous fan off.
Any other ideas please?

you could cool the outside of the intercooler with a fine mist of water , to help cool the inlet charge.


http://www.siliconchip.com.au/cms/A_106213/article.html

 

[Darwin]

the other route was the 200sx turbo and something else... who had a price for that,,, it was 400 quid or so wasn't it

200sx uses a T28 instead of a Terranos T25 , dont think it will work on its own needs some sort of mapping as well

 

[Terranosaurus]

200sx uses a T28 instead of a Terranos T25 , dont think it will work on its own needs some sort of mapping as well

But Makeitfit is looking for improved bottom end torque, he'd be better fitting a smaller not a larger turbo. A larger turbo may increase top end power but it will also have increased lag as it will be harder to spin up.

A supercharge might be one solution. A lot easier to get hold of now they are fitted to more vehicles as standard.

 

[Darwin]

But Makeitfit is looking for improved bottom end torque, he'd be better fitting a smaller not a larger turbo. A larger turbo may increase top end power but it will also have increased lag as it will be harder to spin up.

A supercharge might be one solution. A lot easier to get hold of now they are fitted to more vehicles as standard.

I *think* is actually the same size turbo , it has something internally differnt

bigger compressor wheel ?

 

[Terranosaurus]

I was meaning the internals - IIRC the T25 is 2.5", T28 is 2.8", T3 is 3" etc T3 and above are pysically larger though and use a different housing.

 

[makeitfit]

Right then, this is an overall plan to do list and I'm trying out your collective brain boxes before bashing the wifes card again:sly
I had planned to go T28 (it's a direct replacement and £166 from USA), i/c fan (or this water spray route),viscouse fan off, chipped with "Tunit"(as they can mod the elecs to suit T28), K&N (already in) via "extreme" air intake.
I had read some blurb on diesel dump valves being used to help keep power on while gear changing for example, as I'm not always in a position to left foot brake etc(still learning to keep my face off the windscreen when I use the other foot),toe and heel usually to wet/slippy etc.:augie
As my truck is never going to be a looker anymore it's going to be a bruiser for a while unless I kill it again
Low down power and torque is the main gain I'm after but there's no harm in a bit of Paxo bashing now and again:naughty

 

[extreme-4x4]

clear your garage and spend a week with me working on it

it will be a looker again... even been thinking of plans for yours chum

and its doable cheap

 

[zippy656]

i keep thinking of doing the intercooler fan. i found the download some where else.

 

[Timbo_1975]

Renewed my membership so can fire off again!

Ok, the T25 turbo will be fine for low down torque the OP wants. They can be made to fully spool by about 2000rpm but only by fuelling adjustments- the stock T2 is REALLY underfuelled as it comes from the factory and there just isnt enough exhaust gases to spool it with any ferocity at low revs.

I have a PSI tuning box on mine currently which is adjustable to a point, and I now have plenty of low speed fuelling (and black smoke) when the turbo is not spooled off boost.

A tweak to ~14psi boost on the wastegate rod, or better still a MBC will help even more so, but if you are off roading / slowly moving etc, the intercooler fan makes an enourmous difference (certainly on mine) to its perkyness by keeping the charge temps down.

The T28 turbo is different to the stock T25 in that it has a larger compressor wheel within an internally different housing, and is capable of flowing more air at a lower shaft speed, which is where the T25 is becomes restrictive at higher revs. The exhaust housing and turbine is the same. Fitting the T28 results in less restriction on the exhaust and more airflow through the compressor. The downside is it wont spool up until about 2200rpm

At ~155bhp the stock T25 is at its limit- more boost will not result in more power.

If you go much beyond 250 ft lbs of torque (roughtly that with a chip and 14psi) then the stock clutch will slip, we have proved that with a rolling road session and a dose more fuel to see what happens.

When I have sorted the clutch, I can push it abit more and have a PC-mappable ecu that will be able to control a boost controller so we can dial in more boost and more fuel at higher revs that the T28 is capable of.

Hope this helps.

 

[zippy656]

Timbo_1975 any chanc eof some pics of th einter cooler fan, and what parts you used. so we can all look into it

was thinking might help with towing

 

[Timbo_1975]

It's a very simple addition, will take some photo's.

An 11" fan fits like a glove with the tin plate drilled to secure the fan.

Mine is thermostatically controlled via a temp switch in the inlet manifold which brings the fan on at 50degC. It actually runs quite alot of the time around town, and low speed, probably due to heat soak. I have a manual override switch too.

I also have junked the viscous fan, and have a 16" and a 11" side by side which fit perfectly whilst leaving the viscous coupling still on the waterpump.

They are triggered by a temp sensor in the bottom hose at 70degC, and also by the a/c, to boost airflow across the condensor. Again with a manual override.

 

[makeitfit]

Right up my alley:thumbs Cheers mate, look forward to the pics. Are the thermostats easily sourced from scrap yard or do I need new?

 

[davemud]

Hi ya my engine mods to date

Iam running with the 11" fan mounted on top of the inter cooler, with a manual switch, certainly helps when slow driving off road and when towing in traffic no noticeable difference at motorway speeds.

17" dual speed pacet rad fan 1speed runs via thermostatic control 2nd speed manual control, freed up the engine more free revving but best is lest noise and better fuel economy. Just have to re-fit standard fan when towing in hotter climates

Upgraded the fuel injection using a bob box from diesel bob again switched controlled, have it set to its lowest setting at this time while working on the turbo setup.

Have Built a Custom 3" exhaust system from the turbo back, removing the partial filter from the back of the turbo. Now have over boost the turbo will quickly spool up to 19psi before the ecu shuts down just have to lift of the throttle and away you go again, just working on a limit valve to set max pressure But much much more power with the exhaust fitted. now Looking at a set of silicon turbo pipes as the expansion of the normal pipes is quite a lot

Have fitted grooved front vented discs and upgraded pads helps slow the machine down and improve the stopping power awaiting s/steel flex hoses

davemud