Hi dose anyone know if a variable geometry diesel turbo can be used on a petrol ( bike engine) . Has anyone used this with megasquirt? Reason I ask is I heard the vgt's. Are far superior in terms of lag reduction. Any comments welcome

PPC said years ago in an article about scavenging turbos from the scrapyard that most (all?) diesel turbo's will melt on a petrol engine as they are made of lesser materials.
Diesel exhaust is apparently much cooler.

Find a turbo from a 911 turbo though (997) and you'll be fine! (and skint I would imagine)

I'd have to agree with iank - turbines are made of different materials for Petrol and Diesel engines.

Petrol engines have higher exhaust gas temperatures and will probably destroy a turbine made for a Diesel engine.

I have one, but its a special an aerocharger and has no lag that I have noticed really very good indeed but rare.

So what about lag reduction on a standard petrol turbo. (Controlled with mega squirt) I.e retarding ignition and adding fuel/air to keep turbo spinning off throttle? Anyone successful at getting a similar system working?

http://www.youtube.com/watch?v=IGTMVcoP5tY&feature=youtube_gdata_player

keep the egt under 800c and you wont have any issues with diesel blowers on petrol engines , tuning the vgt part is the issue as you really need to monitor shaft speed to stop them surging on a petrol . for a 1 litre bike engine you need something from a 3 litre diesl engine to make decent power.

i have been running a vgt holset from a 6.7 litre cummins diesel on a 2.0 petrol engine for the last year although holsets have inconel wheels on them .

the tiddly vnt/vgt units on most modern 2.0 diesels are just too small for petrol engine use ,the bigger garret /holsets are made to stand lots of abuse and constant boost so cope well on petrol applications

Thats interesting!javascript:icon(''

Couple of things:

Is it difficult to keep the EGT under 800deg... how is this done usually?

How did you control the vein angle is it on/off or is it a gradual open close? and is it vacuum operation or electronic solenoid?

Im only looking to run low boost pressure 5 - 6 psi as i have high compression 11:1 with the bike engine. Dont want to go down the route of a bigger head gasket piston change ect...

cheers!

Boost lag becomes a problem when the compression ratio is low and the engine is not very powerful without the turbo.

I suspect that with a bike engine running highish compression you will have plenty of power off boost already, which will mean the lag isn't really a problem. The other thing with a bike engine in a car is generally you keep the revs up a bit (i.e. 3kRPM+).

In my install I get 5psi at around 6kRPM with a td04-16T turbo (volvo 850 t5r), which is good for an easy 250bhp.

To my mind a bit of lag makes the whole turbo experience more mental (a good thing).


The other option if you are running low boost would be either a ceramic turbine wheel. Ceramic turbos aren't popular because they break at high boost, but they have a lower moment of inertia so spin up faster. Ball bearing turbos are also an option but are a bit pricey, but supposedly spin up quicker. People have done twin turbo (search nitro on the oldskoolsuzuki site), but I don't think its worth the bother.

cant comment about bike engines as i have no experience but as far as i know no one has developed a solenoid drive for vgt that works yet but it will happen at some point



i use a pair of actuators ,one is vac operated to open the vane when cruising ,the other pushes the vane open when boost starts building . it does work but needs a lot more testing to get a more linear boost rise as it got to 1.7 bar at 4500rpm then cracked a ring land

i would imagine boost control is critical with a high compression bike engine even when running quite low boost too and vane position has a huge effect on boost rise with a vgt turbo .

with the vane fully shut boost rise is very quick but vane position needs to rise in proportion to stop the turbo choking up but if you dont control the rate of rise it can overshoot a lot .

in theory you dont need a wastegate as vane positon can also control peak boost but i used a big external gate as i hit 3 bar followed by two new breather holes in the block



ive ridden a turbo r1 and i didnt think lag was an issue lots of boost low down is sometimes worse than up top as i never had a piston issue until i started trying to run over 1.5 bar below 4500rpm