c.h.i.e.f 's 110 Isuzu county

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Originally Posted by jakeslouw

Is there an "Intro to Turbo Diesels" thread?

I need to get my head around some concepts:

- how to relate CFM at optimal revs to a boost map
- are there any issues with exhaust manifold lengths? (Distances between head exhaust ports and the turbo impeller housing)
- what is the best practice for optimum "power band" tuning (ie: boost off idle, signing off at just below the engine rated peak RPM)
- what is the optimum after-turbo exhaust diameter? is there a formula? is there a similar connection between CFM and RPM and cam duration as experienced in naturally aspirated petrol engines?

Probably this info is somewhere, but hopefully somebody has some threads bookmarked?

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Most compressor maps are done on mass flow (lb/min etc), to work out air flow in mass or volume from rpm, boost and temperature requires quite a lot of work, but there are a few websites setup to plot it all out for you.
Diesel turbo manifolds, all the modern production items are minimal volume for faster response. Pulse converter (4-1 and 4-2-1) options are also available options if you'd like to build one. Feel free to test them all and let us know how you get on.
Turbos have an efficiency curve which you can move up/down the rev range by sizing the whole turbo or changing the size of the turbine housing. Where you want it depends mostly on how you drive the vehicle and where you want it to behave best.
After the turbo the exhaust is simply a drain-pipe. Bigger gives lower backpressure but radiates more heat and noise. It's a compromise. Getting all transitions right is worth a lot.

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Originally Posted by Dougal

Most compressor maps are done on mass flow (lb/min etc), to work out air flow in mass or volume from rpm, boost and temperature requires quite a lot of work, but there are a few websites setup to plot it all out for you.

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Thanks, if you have any links I'd be appreciative.

I'm getting back into turbo diesels again after a while, and now I'd be keen to experiment. I'll be reading everything on 4BTSwaps as well.

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Originally Posted by jakeslouw

Thanks, if you have any links I'd be appreciative.

I'm getting back into turbo diesels again after a while, and now I'd be keen to experiment. I'll be reading everything on 4BTSwaps as well.

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Hop on the Garrett site and have a read of the Turbo Tech info there:
Turbochargers | Turbobygarrett

Steve

I find the Squirrel Performance Turbo Calculator fairly good. It is based on the Garrett method as per Garrett website.

The starting point is required power. Using values that you input for data such as BSFC (0.36 for turbo intercooled diesel, 0.38 for no intercooler), Air/fuel ratio (18 minimum for no diesel smoke), ambient temp, etc.

I calculates the amount of fuel necessary for the HP requested (based on the BSFC input, then the mass flow of air required based on the air/fuel ratio, then boost pressure, air temp volumetric airflow, etc to achieve that mass flow.

It also has built in compressor maps and you can pick up to 6 and see the results overlayed on the maps.

Regarding c.h.e.i.f's turbo I think it will be a good size for around the 300HP mark.

The GTX turbos are Garrett's answer to the better technology that BorgWarner came out with some years earlier. The extended tip compressor impellor reduces inertia for quicker spool, and the compressor inlet has slots to feed in more air after the smaller blades which, with other map width enhancements for a wider compressor map (particularly on the left (surge) side.

Even if it surges, by changing your driving style, such as choice of gear when accelerating hard, to allow the engine to accelerate to revs quicker, you can avoid surge. If on the other hand the engine can't accelerate quick enough (too high a gear) the exhaust gas will be hotter making the turbo spin faster which leads to surge - surge occurs because the air flow from the compressor is more than the engine can take. The other control in your box of tricks to combat surge is to increase the fuel.

My bet is this turbo will work well and not too large when used on a 4BD1T set up for good power.

Thanks John
As you have said about changing driving style to prevent surge that is my first port of call.....as I have said plenty of times before I am more concerned about gearbox being scattered across the road before the turbo or motor this time:angel:
I looked into borgwarner Turbo chargers but getting hold of them is harder than the Garrett (not that I couldn't get a borgwarner) I just went with Garrett this time.however borgwarner seem to have some very interesting design concepts !!

In my previous post, I didn't want to imply that the GTX still is behind BorgWarner (that may depend on which BW turbo). The GTXnnnn is a big improvement over the older GTnnnn now it has introduced similar technology to BW.

Auh ok I'm just impressed with the borgwarner tip speed sensor for some reason hahaha

Can only give the turbo I have a go and see what happens I've been wondering about the smoking down low but once again driving style can help tackle this I presume if not I will investigate into a compensator...

When I get my self into gear and put the BorgWarner 6258 on my bench into my 110 we will be able to compare.

Squirel was great to help me size it up.. it surprised me that the larger in the BW EFR series were unsuitable.

will be good to see some comparisons :D
i looked at the EFR vnt's but the general consensus was if i wanted something reliable dont go vnt's and that was from the distributors them selves but having said that i will probably try and find one in the future to help the larger one dispite what people have said...