Isuzu turbo diesel tuning guide

[reno]

I'll have a look on the old engine for you mate. Should be able to sort you out though.

Reno turns out i left the cats at my mates workshop so i'll sort out going over there in the next couple of days then i'll make you up a de-cat.

cheers chris your a star mate

[Spinbitch]

Got one of them so i'll see what i can knock up next week.
You going to Biling?

[Spinbitch]

Got one of them so i'll see what i can knock up next week.
You going to Biling?

[reno]

i was but not now as my mate jay dropped out, if you knock it up could pass it onto tom? and he can give it neal for me to get off him.

[reno]

chris, anything u need for your astra? parcel shelf?

[reno]

any luck chris? im goin blling now too, will be with the mk3 astras owners club

[Justas]

did anyone fitted rhf3 to 1.7td? I want more power at low rpm,bet friend says that if I fit that turbo,I will brake crankshaft because of power at low speed,is it possible?
and what you think about fitting rhf5 to 1.7td
sorry for gramar mistakes

[Hacula]

Its possible, but i dont know anyone who has tried it. It's a very straightforward swap so you could try to see what it does. I still have an RHF5 laying around which im gonna try to fit this summer. I'll sure post the results here when its done.

[Spinbitch]

Found a cat fella, but struggling to get hold of an exhaust, having to work double shifts till thursday as there's a couple of people off sick.
Gonna try and get it done for you, but may have to post it after Billing as i haven't even started to pack all my stuff for the weekend.

[Aberdeenloon]

Whats the max psi has anyone ran on the 1.5td ? As 22psi does not feel that fast anymore...

[reno]

ok chris, cheers mate, if you dont get it done in time then no worrys will sort postage out with you, cheers

[cidul_52]

could some one tell me exactly how do i link the boost with rpm? i mean the values: for example at 2500 rpm how much it must be the boost value and at 3500 rpm also the value at the boost
thanks!

someone???????????

[opopanax666]

Does anybody know of a rebuild kit for an RHB4-VI72, or is it one of the "unrebuildables"?

[nominous]

OK, so finally after many years of ownership and 100K miles on veg oil I've finally decided to take the plunge and have messed with the fueling and boost.
I'm happy for having done so but there are a few niggles.

This thread is awesome in it's knowledge and experience and I have read it more than once from end to end, but it's a bugger to find the right bits when you need to search it, like every forum anywhere, so hoping someone might drop a hint or two to me please.

My astra runs on straight veg oil. For 3 years it was shop bought but as prices pushed up and I found a suppiler I switched over to using cheaper (and more eco friendly) filtered waste oil.
It runs fine. It dislikes the cold but then I even got it started in the Feb sub zero weather so not complaining. I run a flat plate heat exchanger robbed from an old combi boiler which uses the water from the engine to heat the oil and thus thin it out a bit. I also run a looped return so the hot oil isn't sent back to the tank but flows in a loop through the Injection Pump. Undoubtedly this is why it has a small fuel leak.


I've followed the instructions for the white ring mod, but with further reading around I've done things slightly differently.
I hammered the bump flat on the top of the housing containing the diaphram. If you read or look at a VW diesel pump there is an adjustment bolt here. The arguement is after raising the max fuel (more later) that you should flatten that off so that the boost compensator plunger will come out further and thus reduce the fuel off boost. I don't know exactly where the plunger sits stock but it all seemed reasonable so I gave it a bash.

I also turned up the max fuel screw. 1/4 of a turn and reset the hot idle speed back down.

Running stock boost without having touched the turbo. Car is more responsive. I don't see any black (actually more like a white/grey on veg) smoke out the back of it.
Not a bad mod for the turn of a screw, hammer action and chucking a plastic ring, but also nothing earth shattering.

Turning up the boost.
I had one of these lying around:
Electronic Boost Controller | Turbo Timer | Boost Controllers | BCU+

They get mixed reviews. I installed mine with an analog boost guage so that I could sanity check it and didn't fit the solenoid to start with. Car is boosting up to 11.4PSI maximum stock. The analogue and digital guages are close enough to make me happy with it.
So I fitted the solenoid.
Bit of faffing around setting it up correctly. Tiny turbo means the settings are way off from what it would be on petrol but plenty of adjustment and no doubt room for further tweaking.
I set the low boost to 12PSI with the WG opening 1.5PSI before the max level is reached.
Car comes on boost faster now and is faster at accelerating due to the WG not opening as early as it was when manually controlled.
Still however, it's not spectacular.


Set the high boost setting to 20PSI.
Big change. Car is noticeably quicker now. You certainly get the feeling of being pushed into your seat. It's much faster to accelerate (12ish to 60mph verses 16sec on low boost) but it's not reaching 20PSI. Changed to 21PSI setting and set warning alarm to same. Now reaches higher but still not hitting 20PSI.

Problems.
Boost seems to take a long time to come on. I've read about rotating the boost compensator rod so that the ramp of it to put more fuel into the engine is more aggressive. Apparnetly this shouldbring boost on faster?
There is also adjustment to be had by tightening the "nut" under the spring in the boost compensator which will allow the rod to move when less boostis applied. I'm going to try these to improve the pickup of the car. It's not bad at higher revs, say around 3300rpm, but lower it still sucks like stock.

The other thing I wonder about is messing with the max fuel but also the governer speed setting.
http://forums.vwvortex.com/showthread.php?3107325
I find that I can sustain about 17PSI to 4500rpm. I dare not go much higher. I know it should be ok, but it just doesn't feel right in doing so.
I've read about increasing the max speed setting due to it cutting off fuel supply prematurely. Has anyone done this and can give me some insight please?
Also, at just 20PSI is it worth turning the max fuel screw even more? At high rpm I do see smoke now, but after 4000rpm it's not revving as happily as it was and whilst the boost pressure is still present it's like it's being held back. I can only assume this is down to a lack of fuel?

The other thing is that say if in 4th or 5th gear and hovering around 11PSI on high boost. If I plant the throttle it doesn't always push the PSI higher. I have a LED on the solenoid control so I know if it's active or not and it's not allowing the WG to operate so it's like the car isn't providing the right conditions to increase boost pressure, but only some times !?!?

Anyway. Hope something find this interesting, and hopefully someone else can offer some words of experience.
I'm off to read the thread again for luck

[Jack]

Once you've adjusted the boost, turn the fuel up again to match.

[nominous]

Driving home last night was better than most. it was raining quite hard. The car was a completely different animal. I would imagine due to the cooler temperatures in the air.
I turned the screw another 90 degrees this morning and still no smoke, which suggests more fuel needed still!
But, TBH it didn't feel any faster than previously, when not raining.
It also didn't make any real difference to spin uptime and in fact max psi was reduced!!
So something else probably needs adjusting now too

Going to keep fiddling. The VW site I linked to has some really good VE articles.
Definately need to mess a bit more with the boost compensator plunger, both turning it and winding the spring down for faster reactions.

Also think there is a LOT to be gained from butchering the stock air feed and going for a cone filter. Colder charge temps are definately a source of major improvement going from last nights experience. I've not done it yet as I want to try and maintain a stock look. But I have a spare filter in the garage and some flexible piping so what the hell.

Re-reading this thread last night did help a lot. Both to give me some ideas and dissuade some fears. This has been a reliable motor for me. Longest I've ever owned a car and even tho it was bought as a temporary beater it's been a very faithful if not irritating at times car to own. Just coming to the end of it's life in so far as passing MOT's. So I'd hate to kill it getting power greedy having not done so for 4 years previous

I'm finding the suck it and see approach quite novel. I'm used to tuning petrol cars using a wideband and altering the parameters in ECU's, so this is an intersting journey.

Spare engine on standby in case it goes very pear shaped, but again from reading the thread it seems unless I mess with the pump way too much and cause a run away (has happened to me previously when a diesel decided to burn off it's oil supply!), or try for 30psi ++ there is absolutely nothing to fear.

[Jack]

You say you are used to tuning petrol cars using a wideband: you will probably feel quite apprehensive tuning in such a vague fashion on this engine then, but there is no such thing as "lean" or "rich" on a diesel engine. Apart from excessive EGTs caused by too much fuel, there really is nothing to worry about.

And you're right, colder inlet temperatures make all the difference.

Rest assured these are very reliable engines. I got a lot of earache from my old man about messing with mine as it already had 120,000 miles on it when I bought it, but it went on to do another 40,000 under my ownership running far more power than standard.

[reno]

im running 20psi, it wont make any more then that in my astra, ive removed the white ring, but didnt hammer the dimple down. got a full exhaust from cat back , 2 1/4 inch i think, cone off the turbo and routed up behind the passanger headlight, im running morrette headlights so removed the inner light and fitted a metal air feed from a viper induction system, it goes very well for what it is and in 2nd and 3rd gear at about 2.5 -3.5k rev range you can come off and on throttle and it chatters just like a LET haha, sounds immense and is getting nice cold air and hear the turbo spooling up nice and loud.

how do i make more boost though? does this dimple need hammering, or am i at my peak for the standard cooler? i want to decat it anyway and fit the big frontera intercooler, loweing charge temps as it wont be sat behind the gsi bumper. bit of a weapon in the cold too

[nominous]

Yes, EGT is definately on the cards now for this car.
Feeling around the engine bay it's obvious that cold air needs to be sorted out.
The stock IC is way too small IMHO too for what we are trying to pump through it; The turbo doesn't flow a huge CFM but then again that IC is narrow and it's deeper rather than wider. Plus the fan cowling on the back allow air to hug it on the back side.
I've got a spare TD5 landy IC which will fit across the front of the car so if I can find me a NA intake at the yard on the weekend I'll fit that too.

I had a good drive home last night in the rain as expected.
But once I got home I turned up the fuel a bit more. I'd say that I've got about 150degrees worth added now.

Holy sheet !!!

First time on full throttle in 3rd and it ran straight into the boost warning level. The controller cut the boost back down to 12psi as I had set it to. A good investment there
Reset the warn to 22psi and was sustaining 21psi max so turned hat back down to 20psi.

I think I found a better fueling level now. What a difference it makes. I came into work this morning positively grinning from the drive in. Even surprised someone off the lights who I guess was expecting a standard crappy astra.
It's monsterously faster than it was when stock now.

Still there is a problem with the pressure building in the turbo bit too sloe for my liking.
Also I have a lot of smoking coming from the cam cover vent hose on cold start.
It just billows out from there but when warm it's now really visible.
My intake pipe to the turbo is quite oily.
If I go for a CAI I'm going to have to vent the cam cover tube to below the car.
Is everyone's that bad? Someone please try. Just remove the pipe form the intake before a cold start and judge the smoke from it.

It suggests I have a problem with the PCV system somewhere from what I know of petrols.


I'm still running the stock exhaust, with CAT. I know that needs sorting out. Part way through making a downpipe for a petrol so can use the left overs when that is done with.
Stock zorst is bound to be a major restriction.
If you want to get fancy with it there is a lot to be gained from grinding out the turbine housing to promote better flow into and out of it. Also heat wrapping the DP as a hotter exhaust will move faster away from the turbine exit into your much fatter pipe.




Have you rotated the plunger in the boost compensator yet or wound the spring in?
Hammering the dimple will let it come up higher so less enrichment in off boost conditions which is a good thing if you're adding more fuel to it.

[Jack]

lmao

Glad you're enjoying it mate! Getting rid of the cat will help encourage the turbo to spool up, something I never did on my own car. I would also warn against grinding out the turbing housing, as while it may make it better for flow, you run the risk of the slowing the gas going through it.

[nominous]

Yes, you've certainly got to be careful doing it. The log manifold probably doesn't help either it'd be awesome to build a mini equal length one or at least deliver the pulses so that they are not banging into each other in the log but then it often has the effect of increasing the spool time. A trade off against top end power. I've not really ripped one of these apart much. A shame as I have a spare engine and all ancillaries in the garage, but other projects yadda yadda.
Part of the reason in finally messing with the astra is a plan to stick an Isuzu lump into a Honda early next year when the insurance becomes favourable.
I'll not start a car war about pros/cons over Vaux, but suffice to say I have a lot more experience with them in petrol guise and lots of spare parts.


The VW guys have a screw adjument on the top of their compensator housing (think the pugs do too?). Here is a diagram I found of it:



If you start modding the cone, first by turning it and then by actualy grinding it then their are gains to be had here. The good thing about the VW adjustment is that it lets you move the fuel pin further down the large section of the cone. You run a risk of grounding it out against the lip so need to be careful there, but if you were to mod the cone to smooth out that lip you could add insane levels of fuel for the higher revs but still stop it smoking on idle.

Messing with the star wheels allows the plunger to activate faster, but again here there is need for thought if you change the profile. But it does allow you to go for daft boost levels and still be able to provide the right fueling across the whole range, through trial and error (well you can mesaure the pressure required to move the plunger and calculate according what ramp angle to put on the plunger).

Suffice to say I'm going to find a bigger turbo. I've got a VNT, but it's a GT1549 IIRC form a Civic CDTI. I think needs must, and a GT1749 is what I should be looking for to go VNT with it.

[reno]

been given a massive saab intercooler, but is it going to be too big for the engine to handle? im thinking its far to big and aint going to work?

[tom_moran]

depends how thick it is mush.

[reno]

not that thick, same as a rad mate

[nominous]

Off to the scrap yard tomorrow armed with lots of reading from various forums.
Going to collect a bunch of boost pins and springs from different VE pumps.
Reading about th RHB4 we really got dealt the ****ty card compared to some others around the same displacement of the era.

Also trying for a cheap isuzu pump so I can do a cut away model for messing with the boost pin and seeing its effects.
I have an idea for a mod on the housing using the pug cover.
Bashing the cover plate flat might not have been the move to make and the white ring modis possibly making the best of a bad situation; in an ideal world we wouldn't do it...
Need to find the right cars to check out my theory