Thread: 4BD1T Turbo Sizing and Performance Prediction.

For A.M.

Originally Posted by Dougal

I have almost finished running through two turbo examples on the 4BD1T. I have run these on a compressor and turbine match. This is where I have to match the power generated by the turbine to the power requirements of the compressor.

1. GT2256V VNT used on the merc ML270 (I have one of these turbos).
This turbo has a 0.64 A/R turbine housing and I've assumed the VNT can pull that down to about half the A/R.


2. GT2259 wastegated (used on Hino and Iveco diesels).
This turbo has a 0.56 A/R turbine housing and the compressor can flow about 10% more.

The results are interesting.
Low End.
Essentially the GT2259 turbo still spools just as quick. Both these turbos can provide enough boost to burn 140cc of fuel and produce over 600Nm of torque by 1400rpm.
And the wastegated turbo does with with less drive pressure.

Call it even.

Mid-range.
They are pretty much equal at 2000rpm, the wastegated turbo is running less drive pressure (because the turbine is more efficient without the extra vanes).
They can both provide more boost than needed through the mid-range, for the wastegated turbo that is no problem. You simply use the wastegate to cap boost and this lets the turbine breathe a bit easier.
But the VNT turbo still has to push that exhaust through the same turbine. The only way to get less power from the turbine is lower exhaust temp. The only way to do this is to run extra boost which costs power and spikes the exhaust drive pressure.

By 2,500rpm the VNT is running 5psi more drive pressure than the wastegated turbo.

Winner, the wastegated turbo.

Top End.
The VNT has a smaller compressor, it can only do about 27lb/min which starts to cap power at the 2,700rpm point. Now we've already had to drop off max fuel with this turbo as the turbine starts to spike and not be able to flow all the exhaust at max EGT.
So from here we're continually droppping fuel and boost to stay within the limits of the turbine and compressor.
In fact, we passed peak power (~150kw) at about 2,500rpm and have been losing ever since.
Drive pressures also keep spiking and are over 30psi by 3000rpm. Basically the party is over and it's time to change gear.

The wastegated turbo keeps producing more boost and power to beat the engines dropping VE. The larger compressor doesn't start to cap power until around 3,200rpm. At which point 140cc of diesel will be delivering around 180kw.
Drive pressures are comparable to the VNT, but the boost and power are well head.

Winner. Wastegated GT2259.

Summary GT2256V
Torque over 600Nm from 1400-2400rpm
Max power approx 150kw at 2,500rpm. 27psi here.
Limited by compressor and turbine flow limits.

Summary GT2259
Torque over 600Nm from 1400-2600rpm.
Max power approx 180kw at 3,200rpm. 26psi here.
Limited by compressor flow.

So this size VNT turbo has no real advantage unless you are already limited to lower power through other driveline concerns. We need bigger VNT's for these engines, a GT2359V might do it, but I have no info on those.

Clearly Hino, Iveco and the others running GT2259's on 4-5 litre diesels have already done this work. It's always good to agree with the big boys.

I had a brain fart after posting this and accidentally over-wrote the GT2256V 4BD1T data with GT2256V TD5 data in my spreadsheets.
I only recreated it last night after I dug out my GT2256V turbo and spent a few hours to recreate the numbers on it.
Turns out my version is from a Merc OM612 from the sprinter van. I had previously thought (hoped) it was from the higher power ML mercedes.
This sprinter engine/turbo combination puts out 370Nm of torque and maximum 125kw of power. To acheive this it only needs to deliver 13psi at max power and 15psi at max torque.

Unfortunately the turbine with no wastegate is just too small for the 4BD1T, the only hope of giving it useful top end would be with an external wastegate and to be honest there is no point, the complexity far outweighs the benefits. This turbo would spend most of it's time with the vanes wide open and still choke up past 2,500rpm.

So I'll probably put it up for sale (ideal for a TD5 or 200/300tdi) and look into a more efficient wastegated turbo. The GT2259 is available in Hino versions (as mapped out previously) but also a Volvo/Iveco version with a slightly bigger trim compressor wheel. The TD04HL-19T is also a strong contender, but not having turbine maps for this one makes me a little less confident.

man did I walk into the wrong room. Way under gunned in the grey matter.......... Ill close the door behind me

Nerd alert.
But whilst I'm here, does anyone have an exploded view of a garret gt2260vnt?

This link will take you to a GT2260V rebuild thread with some good pics showing many details.

Thanks john, that's perfect. As suspected, all the seals have disappeared from my kit, I'll just add it to the list

Irish terrorist tried to blow up a bus burnt his lips on the exhaust pipe
Any connection to the ?

AM