Roman's 4GR V6 Carina discussion thread

[xsspeed]

Also, and sorry to fact check,are your numbers right for mean piston speed? I was just doing calcs last night for my rb, using mps=2×stroke x (rpm/60)

Top end revs should see around 25m/s give or take. 4500fps is like 1300m/s?

Or am I misinterpreting what you're showing?

[Roman]

12 hours ago, xsspeed said:

hey dave whats your estimate on weight diff between the 3s and this? I thought you had said something like 50kg but wondered if youd started weighing anything?

Not too sure, havent weighed anything.
However gut feeling is that it wont be meaningfully lighter than a 3S setup. 

Was using this calculator. Was using feet per minute as the units. Sorry if mislabeled it somewhere. 

https://www.omnicalculator.com/physics/piston-speed

RB20 has a nice short stroke and a pretty good rod ratio. 

[xsspeed]

where 4500fps come from then? for a 4gr with 77mm stroke at 10,000rpm youre looking at 25.6m/s, or 82ish fps

[Roman]

It's just a number I pulled out of my ass to show a comparison of engine rpm at that piston speed. 

That was somewhere around max rpm for each of those types of motor. 

As it seems a more meaningful comparison than the other way around (comparing piston speed at a fixed rpm) 

And yes I see I labelled it wrong, should be FPM.

[xsspeed]

duh i should have just checked dividing it by 60

[xsspeed]

also you'll be pleased to know i went down a rabbit hole on engines last night, spotted a contender for someone to tap potential, for a nondescript v8 the 1urfse (lexus ls460) looks like it has potential to apply similar 1nz/4gr logic too assuming those things can translate, geometry is a bit more 2GR so not as rev happy with heavier pistons at 94mm, but 11.8:1 CR, D4S, RR of 1.77

[Roman]

Yeah another thing in favour of 4GR is keeping max torque down a bit so a J160 wont explode behind it.
However that now seems a bit of a moot point that it'll need a gearbox adapter anyway. 
However it'll still be nice to use the J160 as it's got good ratios, and, I've already got some to use.
I'd rather not go to a bigger heavier box if I can help it.

[Hyperblade]

Stick with J160, becoming more popular which is good for parts and some amount of crossover with other variations of it is good. It's a good box. And if worried about torque just do the fix the Silvia guys do something internal which I can't remember specifics of.

[HumberSS]

Throw some nice big rads on the bottom of inlet runners where it meets the base flanges for your final print, just to reduce the stress razors there.

This is such a cool build, one of my favourite cars too. 

[shrike]

6 hours ago, Hyperblade said:

Stick with J160, becoming more popular which is good for parts and some amount of crossover with other variations of it is good. It's a good box. And if worried about torque just do the fix the Silvia guys do something internal which I can't remember specifics of.

@Romanits the circlip mod as a base line 500nm or around 400hp, shotpeening is also involved

https://neatgearboxes.wordpress.com/2014/04/16/nissan-silvia-s15-6-speed-gearbox-circlip-mod/

Neat do it over here but im sure someone in nz would

[GARDRB]

Just convert it to mild hybrid and use the alternatory/drive thing to start it rather than dicking around with starters. Then you can run KERS too

[Stu]

Crank handle start...

[Rhyscar]

Loving your progress on this. Happy to provide 2gr doorts for motivation. They go REAL good 

[keltik]

On 11/03/2023 at 11:21, GARDRB said:

Just convert it to mild hybrid and use the alternatory/drive thing to start it rather than dicking around with starters. Then you can run KERS too

Genius. A modern mans Lucas starter generator

[Yowzer]

The clear option for your valve issue is to throw the 4GR in the trash and run the 2GR, just as nature intended.

[xsspeed]

Keep going, I'm dreaming of 4gr altezza track hacks now

What were valves like in the 1nz, obviously a small bore there too, was there any concern there? Yet again comparing this to rb20 (sorry) this is still a big bore, and 20s will happily rev high (maybe not make more power) so I'm guessing the engine characteristics of small light piston and rod ratio/short stroke count for more in pure rpm stakes, and the valves do enough seeing its smaller air volumes per stroke. 

Hanging out tonsee how this goes

Looks way smaller with covers off!

 

Edit: added pic of one of my rb20det heads, looks like 4gr valve setout was rb inspired puhuhu

[kpr]

2gr with 4gr  crank.  

[xsspeed]

would be interesting to see if you could, I'm guessing either the cranks are mounted higher in a 4gr or the piston compression height is significantly different between the two (or both) to account for such stroke difference. solution is only a custom set of rods away if need be

[Yowzer]

That would give a sweet revving 3.2L.

How much do ya reckon you could bore out the 4gr?

[Yowzer]

I do like how the engine is barely in the car and we're already discussing extensive engine modifications