Thread: 4BD1T Turbo Sizing and Performance Prediction.

Over the years I've built up some calculation spreadsheets to predict engine power and torque from air consumption, boost and efficiency (BSFC). I've had other spreadsheets to predict engine airflow from boost, volumetric efficiency and intercooling.

I had a burst of productivity last night and combined the two. I then set all the variables as close as I could to my 4BD1T using information from 4BD1T factory performance charts, observed boost and fuel pump settings.
These variables have all been set as close as I could estimate to my 4BD1T, it will also apply within reason to 4BD2T and 4BT engines.

Here are the basic variables:
RPM range from 800-3,600rpm in 100rpm steps.
VE starting at 0.9 at idle to 2000rpm, dropping to 0.8 at 3000rpm and 0.74 at 3,600rpm.
BSFC starting at 240g/kwh at idle, minimum of 215g/kwh at 2100-2200rpm and climbing to 257g/kwh at 3,600rpm.
Observed boost hitting 10psi at 1200rpm, 22psi at 2000rpm, 24psi at 2200rpm and dropping from there.
No intercooler, 20C intake temps, sea-level and 60% compressor efficiency.
A/F ratio used was 17:1.

Here are the results:








These aren't perfect, they don't include parasitics such as turbine drive pressure which are dropping more power at higher rpm than shown on the graphs. But they are a good indication. I think it's within 10% of reality at all points.

Now here is where it gets very interesting. That loop shaped plot of PR vs Flow was done to overlay on available compressor maps.

Lets start with the smallest, the old T25 I was running.

Quite a good match.

T28 compressor on the DIY T2560 I'm currently running.

This is looking quite bad. I'm surprised to see it left of the surge line. It appears not all of the rough running I have been experiencing at low rpm and high boost is due to the flywheel. Compressor surge is a concern here.
This is obviously why Garrett don't sell a T28 turbo with a 0.49 A/R turbine housing. It lets you drive it into surge.

GT2259 Compressor. This is the closest to the Hino Turbo that some are running:

This is an excellent fit. It is also a very efficient compressor and the turbine is almost 10% more efficient also.

Holset small turbos. Including the HX25 and HE221:

We have an excellent fit for all of them. The HX25, HX27 and HE221 are perfectly suitable.

Holset large turbos. Including the HY35 and HX35:

None of those other tham the HX30 are a remotely good fit.

Originally Posted by flagg

When I did my matchbot I was more conservative with EGTs.. maxed them out at 720c, and limited boost to 20psi. This limited me to the 6258, although with more tuning I'm sure the 6758 would be possible.

I had fridge-blindness yesterday and couldn't see the EGT fields to change them. Fixed now.
I also went through just now and put in cruise conditions. 8psi boost, 716F EGT (380C), 2000rpm.
The EFR couldn't do it. But I got a match by pulling boost down to 6psi and EGT up to 900F. This puts drive pressure only 1psi above boost.
BorgWarner MatchBot

I'll have to measure backpressure again on my T25 when I reinstall it. It used to push 12-13psi drive pressure for 8psi boost. But I've since fixed some intake piping restrictions.