1HD-T exhaust

[BIG PUMPER]

any of you guys tried out different exhaust systems on your turbo cruisers was thinking of a 3" dumped before the rear diff but heard that they lose a bit top end, would a 2.5" dumped before the rear diff solve the problem and have an even rev range?

[Tapage]

with 3" you could loose a little bit backpressure ( it dosen't really matter in turbo engines anycase ) at low rpm .. but coul be a nice improvement more in the EGT segment ..

I'm running also 2.5" in my 2H turbo coz i like under really low boost down 2k rpm .. just to keep some backpressure ..

[Simo63]

any of you guys tried out different exhaust systems on your turbo cruisers was thinking of a 3" dumped before the rear diff but heard that they lose a bit top end, would a 2.5" dumped before the rear diff solve the problem and have an even rev range?

Hmm I'm not sure about back pressure or how it works (but I would like to see mythbusters look into that one) but it seems logical to me that any pressure or restriction will only slow the turbo down and slow down performance, but meh, I'm no expert.

All I can say is when I changed from a standard exhaust on my 80 series IHDT cruiser to a 3 inch mandrel bent system, the car changed completely. It was so much nicer to drive, revved cleaner and generally performed far better than before, off boost and above boost. With the std pipe it used to get athsma above 2700 rpm and when taking off from the lights required a quick change from 1st to second but with the 3 inch pipe fitted, it revved cleanly up to the redline transforming the way the car drove. And for the same reason it also kept pulling harder, longer when up in the speed and revs.

I think a 3 inch mandrel bent pipe is money well spent on a Turbo Cruiser particularly when you look at the pipe being squashed (by the factory) to fit between the chassis rail and the body above the rear diff ... if you haven't seen that then go out with a torch and have a look at how restricitve the pipe is at this particular point.

[BIG PUMPER]

hey simo does your pipe go all the way to the back or dump before the diff??

[dow50r]

i have a 4 inch dump into 3 inch mandrel and straight through muflers, the idea is to minimise backpressure on a turbo car...the bigger the difference from manifold to dump pipe, the faster the turbo spins.

[Simo63]

hey simo does your pipe go all the way to the back or dump before the diff??

All the way to the back .. it's even got the Grimace chrome tip . Aside from being non road worthy, having a pipe dump before the back of the car creates problems such as soot all over the underneath and back of the car and the very strong likelihood that fumes will or can get into the car. My 80 is used for hard 4WDing but also has to transport the family around as well (like our recent snow trip from Qld to Perisher and back) so I stuck with the full length system. My comp Rangie has a system that stops under the cab .... loud? impractical? Sure but hey it sounds GREAT

[Simo63]

i have a 4 inch dump into 3 inch mandrel and straight through muflers, the idea is to minimise backpressure on a turbo car...the bigger the difference from manifold to dump pipe, the faster the turbo spins.

Yeah that's what I was getting at, I think back pressure is your enemy with a turbo motor. I'm no expert, but it just seems to make sense.

[Tapage]

Ya right .. the backpressure don't help in a turbo engine .. but unless you are running boost from 800 rpm you need a little bit of back pressure for that low range of rpm ...

Just in my case the 3" afect the very low rpm range under 1200 ( that means virtual no boost ) when you are crawling ..

And I crawl at 800 - 900 rpm ..

[turbo42]

Ya right .. the backpressure don't help in a turbo engine .. but unless you are running boost from 800 rpm you need a little bit of back pressure for that low range of rpm ...

Just in my case the 3" afect the very low rpm range under 1200 ( that means virtual no boost ) when you are crawling ..

And I crawl at 800 - 900 rpm ..

That makes no sense at all.

Ok so lets have a think instead of posting for the fun of hearing the keys click.

Turbo Diesel Engine

- Engine creates exhaust gas
- Exhaust gas goes through manifold
- Turbo turns due to exhaust gas flowing by.
- Turbo forces air into engine
- If turbo pushes more air than the engine can use we have boost and everyone is happy.

Now if we have back pressure we have the same cycle except the turbo is going to spool slower as the backpressure will limit the amount of gas which can spool the turbo. This in turn reduces boost which means you get more lag as the turbo takes longer to spool.

Now if we put a big ass exhaust on from turbo back the gas flows through well and the turbo spools well and everything goes well. The size of the air chamber in the turbo is not affected by the exhaust, the larger the dump the quicker the gas which has already been through the turbo can exit the area so the quicker the next lot of gas can spool the turbo and on and on we go.

All this must be applied with some common sense and I am talking very generally, so if you want to pick it apart, that is fine, but I am not going to write a thesis.

If you want boost down low in the 800 – 900 rpm range then you need to run a more restrictive turbo which will spool with less exhaust gas, not a smaller exhaust

[Tapage]

That's make all sense ..

I'm running 2.5" exhaust straight pipe from 2" turbine outlet of my K26.8 turbo ..

I have really no restriction at all .. but if the engine don't need any backpressure, then why uses exhaust pipe . .?

Gonna be enought with the downpipe as much ..

I try to keep my own setup on simple .. coz it's a off roader expedition rig .. so dont have in plans run 2 stage turbo setup or variable vane to reach 8 PSI @ 800 rpm ..

Actually I reach under load 10 PSI@2000 rpm it means I can drive it woithout turbo stress on the engine under 2000rpm most of the time .. and this it's my idea something like little care for my engine ..

The turbo as is it's a restriction in the exaust system ( little one off course ) just wondering what's up if I bypass the turbo and run my engine as NA under 1500 rpm .. with no back pressure at all .. ?

Hey I like this kind of thread ..

[dow50r]

Firstly, 800rpm wont do the bearings any good at all...beware driving at that speed, there is not enough oil ptressure to keep the bigend metal bearings appart.
Second...if yu want more low boost, visit www.lcool.org/technical and follow the pump mods thread. screw the adjustment ontop of the pump 1mm to the right, then test, then 2mm to the left, and then set for the best result....you will end up with boost from 1000rpm.
Also, change the fromt compresser wheel and turbo cover, using 3 litre supra items...they are larger...resulting in more boost lower.

[Tapage]

Actually I don't want boost at lower rpm .. coz I like to drive with un-stresed engine ( no boost at all ) until I really need it ..

How much oil press it's recomended at least .. ?

The Toyota FSM claims for at least 4PSI ( rediculus ! ) at idle and 36 - 62 PSI @ 2000 rpm ..

I'm getting at least 28 PSI at idle and 62PSI @ 2000 rpm ( normal operative engine temp )

[dow50r]

Toyota actually cheat by squashing the exhaust...this means more fuel can be put through the motor to spool turbo early, then it wont overspool because of the added restriction...so you better put a straight through on to destress the motor...if you have those figures, your gauge is faulty, or you have a 1hz with turbo, because the hdt will put out 60 cold and 35 hot if it is a cold day.

[Simo63]

That's make all sense ..

I have really no restriction at all .. but if the engine don't need any backpressure, then why uses exhaust pipe . .?

1. To remove the nasty toxic exhaust gases from the front of the vehicle to the rear (or behind and above the cab as on trucks) hopefully ensuring that the occupants of the vehicle don't become ill or worse from the fumes.
2. To allow the running of mufflers (although this could be done in a smaller length pipe)
3. Most importantly, to meet ADR and road worthy requirements

We've answered his question and that is to go for a 3 inch mandrel bent pipe. If you want to spend the extra coin, also get the larger rear turbo housing outlet/dump pipe too.

[BIG PUMPER]

can you buy those dump pipes off the shelf or is it easy enough to fabricate one yourself?

[jsttry]

How do people get the 3" pipe over the rear axle where the factory squashed pipe is?

Any pics of peoples setups would be nice.

Does anyone make bolt on kits for the 1HD-T or do you just have to get an exhaust shop to fabricate?

[Simo63]

How do people get the 3" pipe over the rear axle where the factory squashed pipe is?

Any pics of peoples setups would be nice.

Does anyone make bolt on kits for the 1HD-T or do you just have to get an exhaust shop to fabricate?

Question 1. Not sure, willhave a look and get back to you
Question 2. Can't post pics 'cos I suck at the internet
Question 3. Yes off the shelf 3 inch mandrel systems are available. I've had 2 fitted to 2 80's I've owned over the years and the first was custom or fabricated and it took nearly all day (but was a beautiful job) and the second was an off the shelf one .. (nowhere near as good a job as the custom job)

Cheers