RD28 Turbo options

[jakeslouw]

So as we might all know, Reenen has dropped one of these RD28s into a Safari.

I can't recall the turbo he used, but if my grey matter hasn't gone too vrot, it was a standard factory turbo?

So for those that don't know the engine, it is a 2800cc straight 6 OHC engine that replaced the LD28, and was a factory option in the Y60 and Y61 (GQ and GU) or otherwise what was known as the Super Safari in some export markets.

The GQ had a standard mechanical pump (Bosch Zexel VE) and mechanical wastegate, the GU had a semi-electronic pump (Bosch VP?) and a mechanical wastegate as far as I know.

The problem was the operational spec of that engine:

91.9 kW at 4400 rpm 255 Nm at 2000 rpm

So as you can see, not a crapload of torque and only available around 2000rpm.

This was a function of the high revving engine : naturally aspirated, this engine produces max power at 4,800rpm and max torques at 2,400rpm, so it was built to rev.

The problem is that this is sub-optimal off road: high rev torque peaks often equate and translate to wheel spin.

So naturally, the Ozzies have already sorted out the problem: a Garrett GT2052 variable vane turbo off of the ZD30. The problem is the vane control and also the boost control and lastly, pump optimisation.

So as a total ignoramus when it comes to diesel turbo charging, here is the issue as I see it:

- more boost without more fuel = very little benefit, but less risk as long as cylinder head pressures are not outside of design specs
- more fuel without more boost = very little benefit, but with the risk of high EGTs and subsequent engine damage
- more fuel with more boost = the Holy Grail within design limits

Now the function of a variable vane turbo (also called a VNT: variable nozzle turbo) is to adapt the compression or aspect ratio to the engine demands using a set of rotating vanes or blades that can rotate their pitch like a variable pitch aircraft propeller. This implies that instead of having either low boost at low revs and high boost at high revs, or high boost at low revs and a wastegated limit at high revs like standard turbos, the VNT can provide decent boost at all revs.

https://en.wikipedia.org/wiki/Variable- ... rbocharger

This means a VNT will give optimum boost at low revs, and suddenly the RD28 can push decent numbers straight off idle. No more lag, torque at low revs, it's a win-win.

But to make use of this broad spread of boost, you need a pump that can provide the correct AFR (air fuel ratio) and never over fuel.

And that's where I'm stuck: vane control, boost control and pump tuning.

[Alex Roux]

If it was possible to tweak the fuel to remain in sync with the VNT, I am sure the Aussies would have figured it out by now.

If you cannot find a solution on their forum, I would not be optimistic...

[davidvdm]

Then there is this guy I follow. VNT on a RD28 build... https://www.youtube.com/channel/UCVx9Jb ... XLw/videos

Another guy I follow. Twin VNT install on a TD42. He used standard wastegate actuators with a pushrod setup to obtain a new "gearing" on the VNT. It's a long "series", but you may get some useful info.... https://www.youtube.com/channel/UCrK2_g ... ndQ/videos

Your trick is if you want more "compensation" from the pump than it's intended design calibration will allow. With a big enough IC, you can give it a bunch more fuel than what those pumps are designed to give in standard trim.

You mention a good point, the same point in fact, that makes a Lexus a useless piece of kit in a offroader, and that is that the power is all in the wrong place. It's a stall or spin type situation when it comes to technical rock crawling type stuff, unless you start messing with gearing of at least 4:1 on the TC. You need to decide what you really want the rig to do. Do you want power, or torque, and where do you want it in the rev range. This is typically the same scenario as suspension builds, you can't have the perfect road going vehicle, and a good offroader.

But I'm really interested to see what you end up doing here, good luck.

[jakeslouw]

If it was possible to tweak the fuel to remain in sync with the VNT, I am sure the Aussies would have figured it out by now.

If you cannot find a solution on their forum, I would not be optimistic...

indeed, so that is where all the search engines end up: patrol4x4.com and nissanpatrol.com.au.....

So digging further, there are some tweaks:

- Pump upgraded from 9mm plungers to 11mm plungers
- add a low pressure fuel pump (helps the standard lift pump and increases supply pressure)
- instead of the pissy little GT2052, go for the GT 2554 or the GT2560
- 3 inch dump pipe to 3 inch straight through exhaust
- manual boost controller
- big front mount IC
- limit the wastegate to dump at 1.1 bar (you can run higher but the head gasket craps itself.........dunno if a Victor Reinz heavy duty gasket and head bolt kit will help)

After this, the only other option is possibly an oil cooler (Reenen is still wondering if this would be beneficial, so I'm wondering as well).

Oh yes and lots of dyno time...........

Dual turbos: I don't see the point for this on this engine and the interlacing of the two is extremely complex and usually requires electronics.
Yes, Land Rover and Toyota have started using them, but those are New Gen CRDi engines with advanced ECUs. Even then, I've seen lots of issues with twin turbos on those vehicles. I reckon well beyond my level of understanding and probably also for 90% of turbo installers in ZA. If I have to start engineering this, I'd rather give up and drop in a TD42T, it will work out cheaper.

[Tinus lotz]

So tell me .....bou jy n reisies kar of n plaas bakkir

[jakeslouw]

So tell me .....bou jy n reisies kar of n plaas bakkir

Franken Bakkie

[Tinus lotz]

Jy sien

[jakeslouw]

As reenen sulke goed kan aanvang, dan kan ander mense ook..........

Ek weet waar 'n modified Safari bakkie staan, dit staan al amper 10 jaar daar, miskien moet ek 'n simpel offer gaan maak.

[Tinus lotz]

Rd 28 werk mooi veral met n turbo

[Tinus lotz]

Maar ek sal eerder td27 gaan