Brian Smith

Hey Craig

What rods and pistons are you going with? Are you going stock bore?

Brian

hinton

FYI, I’ve been told that the TTRS crank pulley is a necessity over 7200 rpm, which is where we will stop with stock cams and the new intake.

As for the crank, I’ve been told the stock crank can handle 600 ft-lbs, so it seems like the rods / pistons are the weak link. I haven’t confirmed exactly how it works yet, but there is potential to just slap RS3 rods and pistons in and have a 500 whp capable setup, which is MORE than enough in a sub 3000# car.

Lastly, my plans have changed a bit. I was initially going to build a high compression / high revving NA engine for version 2 of my build. I’ve now come to my senses and will be going turbo.

I am still planning to get the car running as NA first and doing full track testing. From there, I’m on a quest to find all the limits on the stock NA 944 components.

I just ordered a Holset HX35 turbo. I am going to install it and leave the fuel system alone to figure out where the limits are on the stock 944 fuel pump and 07K injectors. Obviously at the point I’ll be quickly finding out the NA transaxle limits as well.

Should be fun and will help people figure out what all is needed to meet there power goals.

Droops83

The issue with factory RS3 or TTRS pistons is that they are designed for a direct fuel injection (DFI) engine, so they are ~10:1 compression, which is too low for a high-revving NA engine but too high for a port-injected, high-boost turbo engine to run safely. You probably want to be somewhere between 8:1 and 9:1.

Also, (perhaps the Audi experts can chime in here) it would be worth checking if the factory RS3 uses cracked-cap connecting rods (most OEs do), which are really only useful when installed on the exact rod journal they came from when considering how tight the bearing clearances are on these engines.

hinton

The guy I know that used them said his compression ratio was 9:1 with a TTRS head gasket. It must be the combustion chamber that makes the direct injection that high of compression.

As for the cracked caps, to my knowledge they only have to be installed with the rods they came from (for obvious reasons) not the journal.

Droops83

Good to know about the compression ratio.

As for the cracked rods, I guess you'd better hope the are still round as they cannot be resized (for obvious reasons).

GPA951s

When You get your car to Watkins Glen and are coming out of the toe of the boot with 500 HP... You WILL want more... :-)

Cjar

The guy you know must have missed something. VW head cc's at 46, Audi DI head cc's at 45. Jetta head gasket thickness is 0.015", TTRS is 0.031". Both engines run 144mm rods and have 220mm deck height. So if you put TTRS/RS3 pistons in a VW block with TTRS/RS3 head gasket you'll have a CR of 9.68 instead of 10.0:1. Unless he forgot to mention he's running a thicker head gasket (Bar-Tek sells them for the TTRS)? As mentioned, that's much too high for a port injected turbo engine, not to mention TTRS/RS3 pistons have a bowl shape optimized for DI, not port injection.

Running stock TTRS/RS3 rods are fine to 500 lb-ft at the wheels, according to Hank Iroz. I see no issue with whether they are cracked type or not as long as the same cap and rod stay together. The rod bearings for TTRS/RS3 and VW are the same, so as long as you check clearances before you assemble the engine it will all go together fine.

Many good options out there, but I chose to run custom JE pistons, basically the spec Integrated Engineering sells for the VW except with 22mm pins and 9.5:1. I wanted a higher CR to keep the off-boost torque up for daily driver, have access to pump 93 octane here, and have the option of using the Bar-Tek thicker head gasket if I hit knock when upping the boost. The nice thing with a custom tune and older cars here in WI is that I don't need to pass smog, so I can also richen up the fuel to fight knock.

My donor block had a scuffed cylinder, so I went up to 83mm bore. Bore/hone is cheap (compared to buying all these parts), and I can have the piston-wall clearances optimized right away.

Rods I bought a set of H-beam 144x22mm from Integrated Engineering, part# IERHVB2-RD. They quoted them at 125HP (flywheel) each, so plenty for my intended usage. I know they and other good companies offer I-beam for only a bit more money (but more weight).

Craig

hinton

Appreciate the info Craig!

V2Rocket

says who?

the 996 and iirc 997 turbos were 9.4:1 and port injected.

and our dear friend Hellcat comes at 9.5:1, also at the port.

compression can be much higher with a 4V head for a given octane since you don't need anywhere near as much timing advance as a typical 2V.
even moreso for a tiny baby chamber like the 07K has vs the 100mm bore of the 996/997/944.

hinton

The guy I’m talking to worked for Iroz, and on his next build is bumping it to 10:1, whatever that is worth. Different strokes for different folks. If I go the RS3 route it’s strictly because I find a silly deal on them and it fits my budget theme. Regardless, I don’t think I’ll be looking for more than 400whp anytime soon, as that’s what my widebody build is for.

Cjar

That’s true. While larger bores are less susceptible to knock than smaller bores, with modern electronics with knock sensors, variable cam timing and good fuel it makes perfect sense. Makes me feel better about picking 9.5:1 for sure.

Yikes, how much boost? E85?

Anyone upgrading cams? I’m working with CAT Cams on a spec, but for how well the stock 07K head flows I wonder if it’s worthwhile?

4Lo

Ton of great information over the 90 some pages. I'm sure I've missed a number of points as I've been catching up, but if going for a high HP build what would you be looking at cost wise? Say 600-700whp on 93/e85 Was originally looking at a built/supercharged LS, but considering this as an alternative.

Here's what I was assuming after reading parts wise (costs might be a bit high as I just pulled them from IROZ's site since it seemed like a 1 stop shop).

Engine - $500
Pistons - $1170
Rods - $812
Rod bearings - $140
Mainstuds - $250
ARP Headstuds - $190
Valve Spring Kit and Titanium Retainers - $650
Supertech valves - $400
8 bolt crank - $1200
cams ??
-----------------------------
Engine total ~ $5400

Swap setup (Kit, bellhousing, clutch, flywheel) - ~$3000
Manifold, turbo, downpipe, pipework, intercooler etc - $4500? Haven't priced all this out yet in detail.
So looking at almost $13k at that point.

Would the throttle body upgrade be needed?
I assume looking at least a couple more grand between the standalone setup + wiring harness that will be offered, the intake manifold, pedal, and misc other items? Just trying to get an understanding of full parts costs for such a build and what I might be missing or what can be cut out.

Thanks in advance.

hinton

I’ll have to ask... If it were my build, I’d run a thicker head gasket and do meth injection on high boost settings.

As for cams, I know Cat has a few options. The TTRS cams are a drop in upgrade as well, I’m just not sure how big of a difference they make. I’m still learning about this platform!

Cjar

AVL-Schrick has upgrade cams for RS3/TTRS also, but Cat is much less money. I’ll have to look at the charts and see how much lift I have room for without machining too much out of the pistons.

Cjar

600-700whp? For that kind of power $20k is probably in the rear view mirror... I’m targeting 450whp and, granted I’m probably going a bit overkill on the OEM plus mentality, I’ll pass $20k before too long. Could probably cut that back some if you are building a racer and can skip comfort and drivability.