Cossey’s note: This thread is going to be used for any questions anyone on the forum may have about building motors, headwork, and hardware/parts. Like it’s been said before, we have some of the most knowledgable builders in the area on this forum, and I’m sure they’d be more than happy to help out fellow enthusiasts. Please post any questions you may have. Any questions about tuning/ECU’s, please go to the other tuning thread. Thanks in advance guys, and lets keep this thread as clean and informative as possible. /not
I found some RS4 intake cams for sale for my car. I’m wondering what my gains would be with those. My car has the same 2.7L V6 motor as the RS4. Eventually I want to have the same bits around the motor as the RS4, so I’m planning to gradually build towards that.
is it always a must to match cams(not highly agressive grind) with other bits like valve train and crank? im just thinking if i’m going to get the car all unbuttoned, i may as well save more, get my turbos done AND throw in the cams in one day.
valvetrain upgrades are almost always a must with cams, as is tuning.
with your motor since you have to pull it out anyway to change the turbos it wouldnt be a bad idea to do it all at once.
another motor question not tuning lol.
Justin this thread has pretty much gotten nowhere tuning wise not by any fault of your own, was a good idea though. maybe an FAQ would be a better idea.
how much would I need to port the ka24de head to get ~400whp with a 9:1 comp ratio bored out to 90mm (looking into the brian crower stroker kit) with a 57 (gt3076)trim through a 3" exhaust running 20psi? :gay also what would ideal cam duration be?
no i only want mid 300’s at 20psi, do you think i should bore it out more than .20 the cylendar walls are real thick on the ka24 so I could probably could bore it out more if needed to meet my power goals, any input would be nice cuz I’m basically shootin in the dark here.
you cannot get the turbos out without removing the engine. simple as that. the motor mounts connect to the subframe so if you remove the subframe the engine will naturally want to follow it… its not as hard as you think. if youve got the space, time, tools and motivation assuming everything goes along smoothly you can do the entire operation in one full days time. but figure atleast 12-16hours total time to do it. your stock tip tranny wont take to the RS4 power very well for a long period of time. and running RS4 cams, without the RS4 casting heads, and RS4 intake manifold, Y-pipe. etc wont get you full benefits. the cams arent necessary either. there are people running 11.2 on full interior, stock cams, stock bottom end, with tons of boost on a B5 S4… its alot to do with the fueling arrangment, JHM motorsport is who im talking about… but your stock tranny will begin to show signs of weakness with anything more than the chip and turbo back with some spirted driving, dont beleive me, see for yourself and let me know how the tranny responds to a k04 turbo/k04 fueling/software treatment
Trick question. You need not port the head to achieve your target.
First let’s look at the GT30R map:
Assuming 300 feet above sea level, which is roughly here in the capital region, we can state that 14.5psi is the pressure per atmosphere unit measurement.
Therefore (20+14.5)/14.5 = 2.38 pressure ratio. Call it 2.4 for simplicity.
At 6800rpm you’re moving roughly 40lb/min in the KA24DE, assuming a VE of 95% and a lot of other massive assumptions that simplify shit, because my answer is going to be as precise as your question was.
So presto, you end up just kissing the edge of the 78% efficiency island @ 2.4 pr, which means you’ll be within the most efficient zone at redline, at 20psi, at 300ft above sea level.
Given the fact that your head’s smaller ports make for shit flow at high rpms, we can cheat around that a tad by installing cams (and valvesprings) that enjoy the mid to upper RPM range, such as a 264 degree unit. Don’t bother with a 272 - you can’t rev enought to take advantage of it. You’ll probably manage to attain your 400whp (~500bhp) target at 20psi, but who knows what fuel will be necessary. Somewhere in there i’d hope there’s a quality engine management system handling all this. May I never hear the word “SAFC”.
If you choose to stroke the motor, your rod ratio will go to shit and you’ll end up with a truck motor that wants to rev even less than it did, with much greater piston skirt friction and more sensitivity to detonation. You’ll have kickass bigblock style torque that an ATP 2871r or 3071r would absolutely love, but it’ll kill your ability to make horsepower above 5252. Right where the turbocharger really comes into a wonderful spot and the cams start to help things come alive, your pistons would be screaming for surrender.
