1G-GTE+Eaton M90 (or similar...)

**boxh34d** · 10-09-2010, 03:16 PM

Sorry OC, but where did the torque and pressure figures come from in your last post? Me no understand. . .

**oldcorollas** · 10-09-2010, 03:57 PM

power = (torque x rpm ) / 9402
that is basic relation betweenthem

assume a well sorted engine could be 100Nm/L (i, bike engines, high end car engines)... or 100%VE and other engines maybe 90-95Nm/L (ie, 90-95% VE)
not talkign actual real VE, just relative to a well sorted motor.

so.. if you know the power you want, you can calculate the torque needed by that first eqn.

then, using
torque = Nm/L x (1+boost in BAR)
you can work out boost required to make the power you want, for a given fudge factor of efficiency (VE%)

you can apply that method to most car and bike engines, but it just tells you the numbers for your chosen power and rpm (not if your components can actually get there), and is a godo way to sot out rough figures from real world examples (or sort out BS

)

edit: you can reasonably assume that you can take the stock 1G torque figure of Nm/L and use that, or increase it a bit if you have improved manifolds/breathing/stuff, to ork out pretty close ballpark figures

edit2: you can work out engine stuff from both ways..
ie, from fundamental comparison of engine capabilities (like my way) or from a fuel/air usage for a given power way (like you said) and as you can see, they usually meet in the middle.

**mullett** · 10-09-2010, 07:11 PM

Hmmm, can't rep you again yet, but it's deserving. I'll see if one comes up for a reasonable price, but nathans comments have given me hope for the turbo...

-RM

**boxh34d** · 11-09-2010, 08:07 AM

Excellent, thanks very much for that.
Any idea if that figure of 100nm changes for diesel engines?

**oldcorollas** · 11-09-2010, 08:41 AM

no idea for diesels at all but shoudl be easy to work out.

just look around for torque and boost figures from a whole bunch of different motors, then work out the Nm/L and sort them into efficient and not so efficient...

for example, Audi Q7 V12
5.934L, 1000Nm, "up to" 2.6bar absolute (1.6bar boost)
1000/2.6/5.934 = 64.8Nm/L

http://www.audiworld.com/news/05/a8tdi/content.shtml
A8, 4.134L, 650Nm, max boost 2.5bar
if the 2.5bar is absolute, then 62.9Nm/L (if it is 2.5 bar boost, then the Nm/L is worse)

land speed car
http://autospeed.com/cms/title_Diese...2/article.html
4.4L, 1500Nm, 5.2bar absolute = 65.6Nm/L

edit:
SAAB http://www.autoweb.com.au/cms/A_1088...wsarticle.html
1.9L, 400Nm, 1.8bar boost = 75Nm/L... thats a lot higher than the race engines, but a lot smaller motor?

so.. i guess the current pinnacle of diesel performance is about 65Nm/L? with maybe 60Nm/L max for most cars and a bit higher for well developed production diesels?

**mullett** · 11-09-2010, 02:24 PM

Yeah, the whole 'diesels make torque' thing is a bit of a myth...they just don't rev very hard, and have a solid torque band over a narrow rev range...plus they can run LOTS of boost. Non turbo diesels are slugs without massive displacement.

-RM

**oldcorollas** · 11-09-2010, 05:59 PM

off topic but..
i often wonder what diesel fuel consumption is like at full noise compared to same power in a petrol motor.
diesel seems better during cruise/normal cycle, but are they better or worse at WOT?

**mullett** · 11-09-2010, 06:27 PM

I imagine better, a massive compression ratio has to help a lot. Petrol trucks went out of fashion long ago, and I think it was fuel economy that killed them. Trucks spend a lot longer at full-output...

-RM

**boxh34d** · 12-09-2010, 11:19 AM

Those figures seem to add up pretty well. My 2.8L diesel hilux puts out about 180Nm from memory, so close to 65Nm/L.
As for reletive fuel economy, Mullet would be correct. My own hilux compared to a petrol powered one seems more economical at full load, but its nothing definitive.