Roman's 4GR V6 Carina discussion thread

[Roman]

Cant you see I'm doing that enough myself already?! 

[xsspeed]

i think you live for the janky shit

[VitesseEFI]

11 hours ago, Roman said:

Cant you see I'm doing that enough myself already?! 

Value engineering brings its own trials and challenges - it’s all part of the fun 

My own 6 pot ITB project is in a redesign stage after not entirely successful trials (don’t hold balance). Happily the original plenum system works pretty well 🙄

[fuzzy-hair-man]

On 09/11/2025 at 13:58, Roman said:

Yeah my last intake setup had 1x actuator pulling both banks open. 
I was getting frustrated with variations from bank to bank, so I figured that dual ethrottle would solve my problems... Ha! 

Yeah the ethrottle idea is alright, but if I can make it work fitting a gearbox'd motor directly onto the throttle shaft. It eliminates problems from linkages doing weird stuff or more points of backlash etc.

TL;DR: ITB sucks balls for V motors, a single or dual throttle on one or two plenums would have made life considerably easier

The following might be of some interest, not sure but skip to about 10mins.

 

[xsspeed]

until the wat kicks in?

[Roman]

We all know that I'm keen to creep the limiter up. haha. 

But I would also like to at least attend drag day first. 

Currently 9500 limiter so it starts doing stuff at 9300ish.

[BiTurbo228]

Man that looks impressive!

Can you feel that big ol dip and rise in the power curve?

[Roman]

Not at this stage. Too busy anticipating parts falling off / flying out / etc to notice details like that. Haha

I want to try some slightly shorter runners and push that bump over to the right a little more hopefully. 
But that will drag the dip with it too. 

I can possibly mitigate it with VVT or something. Maybe test a variable runner or dual runner length eventually.

But for now, I'm super stoked with it! 
 

[BiTurbo228]

Shifting it around might help flatten it out too, if it matches better with whatever pressure wave fuckery is going on in the exhaust. Who knows? Not me!

[BiTurbo228]

Also, if those estimated power figures are anywhere near true, and you can smooth out that bump, KPR might need to start looking over his shoulder...

I also might humbly suggest you find an E90 M3 that thinks they're hot (in case you wanted a comparison with a pretty rapid factory stock car)

[Roman]

Theres no comparison to any modern car if its got a dsg box. Even if its got less power the difference it makes is insane.

But its about the experience not the outright performance! 

In most ways my daily driver is a much better car.

Its funny how often you see people whos tow car is a significantly faster than the car on the trailer.

But often the more powerful car lacks the same grin factor. 

[Roman]

8 hours ago, BiTurbo228 said:

Shifting it around might help flatten it out too, if it matches better with whatever pressure wave fuckery is going on in the exhaust. Who knows? Not me!

Yep this is one of those things where all the calculations in the world wont help. Just need to test and experiment.

The "dip" is still more power than it had previously anyway! 

[tortron]

2 hours ago, Roman said:

Theres no comparison to any modern car if its got a dsg box. 

But its about the experience

[kpr]

22 hours ago, Roman said:

Not at this stage. Too busy anticipating parts falling off / flying out / etc to notice details like that. Haha

I want to try some slightly shorter runners and push that bump over to the right a little more hopefully. 
But that will drag the dip with it too. 

I can possibly mitigate it with VVT or something. Maybe test a variable runner or dual runner length eventually.

But for now, I'm super stoked with it! 
 

 

Probably find the dip will get a whole lot better  with a runner length change.  Likely the intake and exhaust are doing bad stuff at the same time.  

 

[BiTurbo228]

On 14/11/2025 at 20:25, Roman said:

Theres no comparison to any modern car if its got a dsg box. Even if its got less power the difference it makes is insane.

But its about the experience not the outright performance! 

In most ways my daily driver is a much better car.

Its funny how often you see people whos tow car is a significantly faster than the car on the trailer.

But often the more powerful car lacks the same grin factor. 

Oh, yeah, that's a manual E90 M3 in the graph. Best flag them down to make sure they're in a 6-speed before you race them

Point was more that any 80s car that even comes close to beating an E90 M3 in a drag race is a bloody fast car. DSG or not.

[VitesseEFI]

Sounds EPIC from inside 👏👍🏻

Sees to go pretty well too 🙂

[mjrstar]

My rough rule of thumb is you want around 90kph at the shift point in second gear.

Can you play with tyre diameter a bit to work in your favour. ( thinking a 225 wide 13 inch)

[Roman]

My drag tyres are a 205/65/13 or 205/60/13 (cant remember) 

But a fair bit smaller diameter. But doesnt really help toooo much.

Cant buy these tyres anymore though, so once these are cooked I need to move onto the next best option. 

Which is the 225/50/15 Hoosier which is even bigger dia. 

I've got a 4.77 final drive tucked away, that I was planning to swap to. 

But after this drag day I think I might order a 5.3 from Weir. 

Although my cruising rpm will suffer, it's going to be dumb being unable to use the cool gearing stack of 3-4-5-6.

[BiTurbo228]

Man that sounds good.

What sort of trap speed are you thinking you'll get? If it's ~90mph then the 4.77 will put you around redline in 3rd. Any higher and you'll have to grab 4th which might slow you down just as you get to the line. The 5.33 diff is around the top of 4th at 90mph. Obviously with stronger acceleration all the way there. How fast can you change gear?

If I could get my average acceleration stuff sorted on those graphs I made I could probably give you a guide as to whether the acceleration gained offsets the gear changes, but that's proving difficult (500rpm increments in the data isn't fine enough).

Oh, and you're currently at 3900rpm at 70mph. 4.77 diff will be 4400rpm. 5.3 diff will be 4900rpm. How much cruising vs drags are you going to be doing? S15 J160s have a 0.767 6th (I think) which is a bit longer, making it 3500rpm with the 4.3, 3900rpm with the 4.77, and 4300rpm with the 5.3. If that makes any difference to you.

[Roman]

If this car only does 90mph over the line I'm gonna set it on fire. haha. 

The Echo did 100.99mph 

Hold the line caller, will find the graph