I had my 13bt powered Land Rover on a dyno

[Nz Nath]

I booked my 47year old Land Rover onto a dyno day, amongst a bunch of ricers.

The landy runs a 13bt and h55f/splitcase, with 4.11 diffs and 34” super swampers. Holset turbo, 10mm inline pump.

The torque numbers are about what I was expecting based on a bum dyno comparison to modern common rails. I was actually expecting slightly higher peak power, but on the graph we can see torque absolutely plummets by 50% from peak torque to theoretical peak power, flatlining the power plot. From the dyno graphs I’ve seen that’s a bit unusual? I’ll hopefully get the chance to put it back on the same dyno after going twinscroll so it will be interesting to see how much of that torque drop off is down to high EMP.

 

[Dougal]

Fit some smoother tyres and you might be more accurate again.

The shape is roughly what I'd expect. Disconnect your snorkel and air-box for a run to see how much restriction they're causing.

 

[Nz Nath]

There wasn't really the option to experiment with anything due to the dyno day format, they had over 20 cars to run. Reflected in the price though, $100nzd per vehicle is not a lot of money for 4 staff and the dyno itself. I don't think they're doing it for the money.

I have a set of 31" ATs, but I left the 34s on as that's what I'll always be running normally. I would be very interested to see the result of the smaller tyres, but I think paying for "real" dyno time is not cheap. The same for the intake setup, I'd love to experiment and see what difference I'd get. I doubt it would be much though, that's 4" to the airbox exit then a smooth reduction to the 3" turbo inlet. All the welds ground flush internally and the airbox inlet bellmouthed, large unifilter pod etc etc


To be honest prior to fitting the he221w the 13bt always felt asthmatic at higher revs, even with the 5.5cm housing it outperforms the ct26 and ct20b turbos significantly at higher revs as well as low down. Maybe the cylinder head just flows that poorly? I'm reasonably confident the injection pump holds fueling up to 3400rpm, yet on that graph the torque is already dropping at a similar rate from 2400rpm. For boost and and fueling to stay the same, but torque to drop, what other factors are there? What percentage VE drop would that equate to?

A few members have posted about port polishing, but never really gave any feedback afterwards. My intercooler is a cheap Scarles one, but I noticed a decent EGT drop when I fitted it, replacing some kind of junkyard stock cooler. Besides exhaust pressure what else comes into play to explain the torque drop?

 

[Dougal]

The things against turbo diesels as rpm rises:
1. Diesel burn speed. As you go faster the pistons outrun the slower part of the burn which drops cylinder pressure.
2. Injection time. As you go faster your injection window and ignition delay become bigger problems. Only so much timing advance will help.
3. V.E droppping
4. Turbo drive pressure climbing.
5. Intake losses.

I've got a Donaldson Informer restriction gauge and it's really interesting. I have a big donaldson housing and even that shows a bit of pressure loss.

Workshop next to me has both chassis dyno (2 wheel roller type) and an engine cell dyno. But I haven't used either on my own stuff.

 

[Nz Nath]

Something doesn't seem right with that torque drop though, the common toyota diesels you might see dyno print outs for always manage to easily keep power climbing past peak torque. Common engines would be 1hd***, 1vdt, 1kz, 1kd.

Sure the common rails can be doing clever stuff with injection timing etc. But I'm running static timing about 3deg advanced from stock, and with the 10mm elements I should be getting the fuel in quick. Maybe I should try to have a look at the timing advance unit, I did read somewhere that they can stick/seize.

 

[relaxedcruiser]

Well done Nath, I love your enthusiasm !
Makes me want to dyno my 12ht aswell - would be interesting to get those figures.

 

[Dougal]

Something doesn't seem right with that torque drop though, the common toyota diesels you might see dyno print outs for always manage to easily keep power climbing past peak torque. Common engines would be 1hd***, 1vdt, 1kz, 1kd.

Sure the common rails can be doing clever stuff with injection timing etc. But I'm running static timing about 3deg advanced from stock, and with the 10mm elements I should be getting the fuel in quick. Maybe I should try to have a look at the timing advance unit, I did read somewhere that they can stick/seize.

Those engines are all shorter stroke and shorter stroke means higher rpm before power drops off. It's all about piston speed which is determined by rpm and stroke length. My 4BD1T and my VW 2.0tdi both make peak power at the same piston speed. But the Isuzu is 3200 rpm and the VW is 4000rpm.

Big 4 cylinders are sluggers.