1HDT revs and boost

[Jungle]

Ok the manual gearbox is in and its working a treat.

What i've really noticed since the conversion is the boost and the rpms at highway speed.

At around 100 km road speed or 85 kph on the speedo the rpms are approx 2300 i n fifth gear. Does that seem about right for other manual 1HDT diesels. I thought it was a bit high. Much higher than my 12HT which is around 1900 in fifth gear. Both trucks are running on 35 inch tyres.

The other concern is that the turbo boost doesn't reach full boost of 10psi until 1800 rpm. Seems a bit late to me. Keen to hear from anyone who has some real specs on these or just some good old fashioned experience. I reckon the boost should come on at 1200 of even 1500rpm.

Any thoughts?

Jungle

[doddzee]

The 24v manual 1hdt im driving at the moment does 100kph at 2400rpm on 33's so think your revs are probly about right. What gear ratios you running?

The turbo used to be like yours reaching full boost at about 1800. We took it down to a diesel specialist who got it down to 1400 ish rpm. Not sure how sorry but it made a huge difference no more changing down on winding hills.

[sig]

talk to wopass he has tweaked his fuel pump to shift the boost down lower in the rev range.cant remember what revs mine pulls at 100kph .i,ll check at the weekend when i take it for a fanging

[skid]

hey George, somewhere on here , not too long ago, all of this revving chat was discussed.

my manual on 33s is about 2600 at 100kph and the little green light comes on about 1800 I think

if I remember I will check the green light thingy on the way to work tomorrow.


I'm fairly sure in the other thread that everyone was similar to 2400-2600 at 100kph

[Jungle]

Glad to hear i'm not out there on my own.

I have a plan on how to get my boost at a lower rev. Just need to whip down to Az and get him to put a CT20 exhaust wheel into my CT26 turbo. Keep the compressor wheel the same but will get the turbo spooling up earlier with smaller lighter exhaust wheel.

Not sure how changing your fuel pump can bring your boost down the rev range. Keen to hear that one.

How do these trucks go off road if the boost comes in so late. The Torque must not kick in till 2000 revs. Do you have to keep the revs up on them. I'll be running 4.1 diffs. Don't wanna go any lower ratio as the top end revs will be even higher.

Looks like I've got some learning to do.

Cheers
G

[Jungle]

just edited my last post. Got my exhaust wheel and compressor wheel around the wrong way.

Think i got it right this time.

G

[xorph]

I dont reckon its such an issue really, the 1hdt has a bigger rev range than the 12ht so you can get away with a lower gear and rev it out further. it is a bit annoying though.
My 1hz has a turbo from a supra which is the same as std cruisers. these turbos are suitable for supplying about 280hp on a supra. they are a bit big for a cruiser but this aids highway economy. they are huge!
i put a guage on my 12ht cruiser and on my 1hz cruiser. the 12ht has 8psi at just under 1600 and 4 psi at only 1300 i think.
it was a very meaty engine and had big bottom end torque but lost it early.
the 1hz gets 4 psi about 1600 and doesnt get 8psi till about 1900. it has less bottom end torque but midrange torque is higher and has significantly more power.

i never got round to changing the std exhaust, aparently this makes a reasonable difference.

what box are you using? the old boxes (H55) have a lower first gear and in low first it is virtually impossible to stall even with 35s

[Jungle]

Its bloody good having the 12HT and 1HDT to compare. They are both running a CT26 turbo which is what has me baffled. They must have some significant internal differences. Will go talk to my expert later on today.

I have heard bad things about the petrol CT26 as it runs a ceramic exhaust wheel and this has been known to fall into lots of pieces when used in the diesel application. The diesel CT26 runs a steel wheel. Still not completely sure why the ceramic wheel falls apart. You've obviously had a good run with them xorph.

I really need to find out the exact number of the gearbox. I'm assuming its the 1991 80 series box as it bolts up to the full time transfer case. Its definitely different to the H55F in the 60 series.

Will be back with more info soon.

G

[Jungle]

More good info.

More fuel when there's no airflow at the start will help get the turbo spinning a little earlier.
Will attempt doing this later today.

The experts say that the CT26 for 12HT and 1HDT are exactly the same in its components so the differences must be in the airflow and fuel feed rate.

I was told that the Garrett T04 could be a good choice to get the turbo spooling up earlier.

Live and learn!!!!

G

[wopass]

if you screw up the offboost fuel compensator which is the diaphragm on the top of the pump(allen grub screw ith lock nut,screw it in a bit and try it 1/4 turn at a time) your boost will come in earlier as the pump dumps more fuel in at lower revs and thus gets you spooling quicker.

i think the manual is slower to spool than the auto as it doesnt rev up thru the slush box,however you can just slip the clutch a bit if you need to get going in a hurry.

mines the 24v and running 285/75/16's pulls 2400rpm at 100kph

hope thats of some help

[KiwiBacon]

Glad to hear i'm not out there on my own.

I have a plan on how to get my boost at a lower rev. Just need to whip down to Az and get him to put a CT20 exhaust wheel into my CT26 turbo. Keep the compressor wheel the same but will get the turbo spooling up earlier with smaller lighter exhaust wheel.

Not sure how changing your fuel pump can bring your boost down the rev range. Keen to hear that one.

How do these trucks go off road if the boost comes in so late. The Torque must not kick in till 2000 revs. Do you have to keep the revs up on them. I'll be running 4.1 diffs. Don't wanna go any lower ratio as the top end revs will be even higher.

Looks like I've got some learning to do.

Cheers
G

I wouldn't do that.
The CT20 housing is too small, the extra backpressure it creates could float valves and kill your engine.
A variable vane turbo is the only way you'll get a wider boost curve than what you've currently got. A ball bearing turbo will spin up a little sooner.

Changing the settings on the fuel pump aneroid can spin up your turbo sooner, at the price of more black smoke until your turbo builds the needed boost.

[xorph]

The CT26 I used is a Supra one. It is different to the Celica ones. It has the large wheels, and the exhaust is Steel not ceramic, they are the same part as the landcruiser ct26.

I better choice if you are very keen on more bottom end might be a TD05H or a VF23 (like some Sti subs have)

[KiwiBacon]

The CT26 I used is a Supra one. It is different to the Celica ones. It has the large wheels, and the exhaust is Steel not ceramic, they are the same part as the landcruiser ct26.

I better choice if you are very keen on more bottom end might be a TD05H or a VF23 (like some Sti subs have)

How did the supra one compare to the landcruiser CT26? I'd expect it to be a little bigger so boost a bit later.

[xorph]

I meant the supra one IS a landcruiser one. they are known as a 'big' ct26. they even have the same A/R ratio (according to research I did which may be incorrect)
the ones with the ceramic turbine came out in celicas and have smaller wheelsa and a split pulse exhaust housing.
the supra/landcruiser ones are large and very robust. not really a performance turbo as the wheels have a lot of inertia.
the celica ones have a ceramic exhaust wheel that tends to break off but is lighter so has less lag.

[red-devil]

in the VX we have a auto tranns but at 100kph we pulling about 2000 rpm and the boost come in at 1200 rpm

jono

[Andrew1706]

My manual 1HDT on standard 31s pulls around 2800rpm at 100kmh.

When I get my 35s fitted this weekend I'll chuck them on to see how they do.

What is the standard boost on a 1HDT? I haven't fitted a boost gauge yet but I can definately feel a lot of lag.

[KiwiBacon]

I meant the supra one IS a landcruiser one. they are known as a 'big' ct26. they even have the same A/R ratio (according to research I did which may be incorrect)
the ones with the ceramic turbine came out in celicas and have smaller wheelsa and a split pulse exhaust housing.
the supra/landcruiser ones are large and very robust. not really a performance turbo as the wheels have a lot of inertia.
the celica ones have a ceramic exhaust wheel that tends to break off but is lighter so has less lag.

Melett show a different part number for the landcruiser and supra CT26 exhaust housings. They also list different compressor wheels. The exhaust wheel is the same though.
Melett do have the information on the A/R ratio of the housings, but they don't share. I did ask though.

[xorph]

ok, guess they are a bit different, this would explain why Im not getting full boost till a bit later than standard turbo cruisers.

the 1hz/1hdt have different tuning than the old 2H motors, they must have a bit more cam overlap and the intake manifold branches length tuned for midrange. even without the turbo the 1hz feels like it comes on boost at about 2000rpm. old 2H diesels produce max torque straight from idle pretty much.
compared to a modern diesel a 1hz is still a tractor engine and has loads of bottom end grunt.

[wopass]

What is the standard boost on a 1HDT? I haven't fitted a boost gauge yet but I can definately feel a lot of lag.

standard boost is 10 - 11psi. add a boost controller and screw it up to 15psi safely so ive been told

[skid]

What is the standard boost on a 1HDT? I haven't fitted a boost gauge yet but I can definately feel a lot of lag.

standard boost is 10 - 11psi. add a boost controller and screw it up to 15psi safely so ive been told

talking to yaself again Wop

[Jungle]

More testing underway. Took the truck down to Napier last night and back tonight. Went really well. I've just got used to keeping those revs up higher to make sure its producing full boost. Spot on at 11psi.

I took the top off the aneroid thingy and found that the previous owner had already set it to full. I'd never noticed to much black smoke out the back before so was quite surprised to find it wound out already.

Might just keep the turbo for the mean time and put a bigger exhaust system on it. Might also fix the leaking clutch master cylinder before all the paint falls off the firewall.

Thanks for all the info guys. Been a great help.

G

[adogg]

check out this link,I know it says 1hdft but its the same pump,I did these adjustments to mine and it made a big difference

http://www.lcool.org/technical/80_serie ... p_adj.html

[suzolla]

Just another speedo versus revs comparison.
Mine is a 91 VX auto
At 100 km/hr it is doing 2300 rpm
At 2800 rpm it is doing 125 km/hr
Tyre size will not affect this unless the speedo has been recalibrated.

Thanks
Tim