poormxdad

Gentlemen,

As a follow up to a couple of other threads, I replaced my tiny, beat up Kraftwerks-supplied intercooler with a Vibrant unit, and I took the opportunity to replace the 1.75" pre-intercooler tubing with some 2.0" tubing. The output port on the C30-74 is 2.0". As supplied, the Kraftwerks kit came with a reducer right off the Rotrex. I've done some autotuning, and some tuning via log review. Here's a comparison. Just for truth in advertising, I also replaced the recirc valve. Left side is the current tune with the 2.0" tubing.

The car pulls noticeably better, despite extra weight in the front, and boost is coming on sooner. I got a max of 9.3 pounds, which is about a 0.6 pound increase over what I remember getting last November.

HarryB

That reducer KW provides is just stupid; guess they do it for routing/packaging. Did you upgraded to another recirc valve or a BOV?

lbatalha

I don't think the 1.75 tubing hurts it that much, it's more to do with an intercooler that isn't garbage. The KW 2"->1.75" adapter is quite short which is not ideal. In my setup I have a very long 2" to 1.75" 45 degree silicone tube that connects the rotrex to cut kraftwerks tubing (I only didn't cut the L shaped tube). I am routing the whole thing via the hole behind the headlight. I used the shorty KW 1.75->2 adapter on the intercooler intake as there the abruptness doesn't matter as much. This routing is also much smoother. Im using 2.5" on the hot side as that is what was readily available locally.

poormxdad

I honestly believe it's the tubing size. When I got the Kraftwerks kit in 2015, I already had a MegaSquirt. The kit came with a decent bracket that held the MAF and pre-Rotrex intake tubing in place. I gutted a junkyard MAF and bolted everything up, while working towards a real hot side, cold air intake. Removing the MAF provided a similar increase in boost to enlargificating the tubing, and a similar need for more fuel across the entire VE Table.

I get my cold air from that hole under the driver's headlight.

I purchased the Type 10 Universal BOV from Silicone Intakes. She idles now at about 30kPa, which is a couple of units lower than I was able to get in the past.

lbatalha

Good to know. I do plan to upgrade to 2" at some point, but almost certainly not at 9psi, and only after seeing how much power I make with the 75mm pulley. (trying to keep 5speed and stock-ish motor)

I would like to actually check the difference in pressure across the radiator. According to others locally who have installed this kit, I am making about the same pressure at the manifold they did with the KW radiator and tubing so thats a good sign.

EDIT: its weird that you are only making 9psi with the 80mm pulley, can you post some logs?

I am making 0.62bar/9psi/162kpa at 7200rpm with the 85mm pulley, EUDM VVT engine with RB manifold and midpipe (no cat, large but straight through 2.5" muffler), squaretop, stock TB.

bigb5031

Found this thread late last year and I'm back to post results. In early 2019 I installed a built motor with a rotrex c30-94 and reused my original intercooler pipes that came with the kraftwerks c30-74 kit. I was expecting 300hp but only was able to make 263hp. The car preformed great but I knew it could do better. I never knew about the kraftwerks reducer till I saw this thread. Then I also remembered; when I got a larger intercooler, years ago, I was in my early car modding stages so I only pushed the old kraftwerks pipes into each other. The overlap of a 1.75 pipe pushed into a 2.5 inch pipe could have also hurt flow and potential power.

Over winter, I removed power steering so I could clock the rotrex straight down and redo the original kraftwerks hotside intercooler pipes. Was able to run 2in pipe that is about 2/3 the length with 3 less bends. Pipes are from a cheap ebay universal intercooler kit. (sorry if pictures aren't sized well, I almost never post anything)






Was finally able to get on the dyno yesterday, just had to wear a mask while we were there. The first pull on the old tune was promising, made 278hp on it's first run. My tuner commented that it's good I haven't been beating on it because he had to add fuel almost everywhere. We hit some ecu limiters that we had to play with, and still playing with some (fm221) Ecu was/is stopping the show just above 6.7k but even only at 67xx rpms we made about 40 hp more! With a few hundred RPM's still to go, I like to think it'll be more in the 310hp range. What a major improvement for such a small change.


All done on pump 93, the same dyno, same tuner and tuned on the safe side for track days
Red 2013: c30-74 85mm pulley, stock vvt motor, kraftwerks full kit, axle back exhaust, AEM piggy back ecu (later went to smaller pulley but only street tuned it)
Blue 2019: c30-94 90mm pulley, built motor 9.5cr, light head work, full exhaust, square top, fm221 ecu (told him to stop at 7k, blower over spins after 7.2k)
Green 2020: Same mods but no power steering and larger/shorter intercooler pipes (some ECU limiter stopped us at 6.7k)

I'm surprised how early it started making more power than in 2019. This shows me even the c30-74 users should benefit from larger pipes since I started seeing restrictions well below the power level the 74 can make. Defiantly worth doing and thanks OP for pointing out that reducer that got my mind thinking!

Edit: Before was making 14.5 psi and we now saw 15psi at a slightly lower rpm

andym

You mention removing power steering but you didn't mention AC. Were you able to clock the rotrex straight down and keep ac?

jtt

Awesome update! When you clocked the rotrex down, how much clearance did you have between inlet and header?

bigb5031

Sorry, I didn't mention ac because mine has been long gone. It's easy enough to clock the rotrex (I watched a guy on YouTube do it first) You could easily test it out next time your bored or already taking it off to work on something else.


The inlet has plenty and the same amount of room. I'm guessing you might have meant the outlet. It's definitely pretty close. Maybe a inch or inch and a half away. I do have the TRD header blanket between them. The blanket leaves no air gap tho, not sure if actually helping. But either way, I'd bet it's still cooler than any turbo application.

andym

I haven't mounted my rotrex unit yet but i've wondered if i clocked it similar to yours but one rotation toward the driver side instead if I can fit it with my ac compressor for better intercooler piping.

bigb5031

I barely recall it but I think one rotation towards the driver's side put the outlet too close to the body. Not enough room to get a coupler on it, may be able to do some cutting to make things work.
Best of luck to ya, it's all part of the fun.

jtt

Thank you for the pic! After my last tune with 2inch tubing, I'm tempted to replace the hotside with 2.5 inch piping. Buddy and I are making bets if this will increase flow even further . With the rotrex clocked down, I'm in the same boat as you with header -> tdr blanket -> rotrex outlet. There might be enough room to run a 2-> 2.5 inch coupler, but will come back with more info. :-)