G'day all,
If i can get the money together, I'd love to have a crack at doing some decent Natural Aspirated work to my XR6. Until then, I've started doing research and working out what I would like to aim for. I ended up with 2 fairly detailed Excel spreadsheets with loads of data and calculations. More specifically, I ended up creating a 'target' dyno graph that I wanted to aim for. Although you can't just say "I want that dyno graph," throw some money at a tuner and expect it to happen, I made a target so when I do my mods, they all work together a bit better.

So, by my estimates (educated estimates), if I can get a peak torque of 450-470Nm somewhere between 4500-5000rpm, then I'll be looking at a quarter mile time of around low 14's to 14 flat. Assuming the torque curve doesn't get too peaky. My engine stock produces 372Nm at 3500rpm so thats the base point.

The reason I'm posting this here is, I wanted to see what you guys would think it would take to get the above figures. My starting point is:
-Proper CAI (eg GnD Box, BA XR8 Pod box, F6 intake box)
-3 inch intake piping (or similar)
-Head porting
-Custom Regrind Cam
-Extractors
-2.5-3 inch exhaust w/ 3 inch cat
-Shaved Head
-Custom Edit (Flash Tune)
-Uprated ignition
-XR6T injectors
-XR6T fuel regulator
-Performance ignition leads

I reckon the above modifications would be good for about 420-430Nm so tell me what you would add or change. Write your list of what you would do and tell us what you reckon you would get. I'm not much interested in power figures, its torque that gives acceleration.

UNDERSTAND THAT THIS IS A HYPOTHETICAL INVESTIGATION. PLEASE NO "YOU'RE AN IDIOT, ITS NOT POSSIBLE" POSTS. I've also read many tech documents on modifying the I6 so I know whats in them already.

Look forward to the responses.

well, since power to derived from torque ill just give you another measurement.

for 450nm @ engine @ 4500rpm you will need ~212kw @ engine @ 4500rpm

And cost u round 11K

posible

start saving as the saloon cars get that and in ea's at 1450 kg they run mid to low 13's

expect a lot more work than you mention!

something else to think about, im assuming your talking about the car in your sig?

its hard to get hold of reground vct cams.. you may have to send your own cam to get ground (except for the cam being off the road, you wanna hope you get the right profile) so just be aware of that,

but with the appropriate headwork and cams and ecu support low 14's should be more than achievable..



-mitch

Yeah, I know. I deliberatley didn't mention everything I could think of for people to add what they think. I would expect at the very least a comprehensive rebuild on top of that.


Yeah, I know. But in the magical world of hypotheticals, money is no problem.


Yeah, that sounds about right Gaz. Assuming there is even a little bit of meat to the curve, that should be accompanied by a peak of around 225-240kW at the engine around 1000-1200 rpm higher. Depending on the actual curve though.

mitchg911, I'm doing my own research on cams in my spare time and I'm also investigating the BA/BF VCT mechanism. (Thinking about final project for my mechanical engineering degree.... )

Everyone seems really tight lipped on this. Seriously guys, tell me what you think it would take to get 450Nm at the flywheel at around 4500-5000rpm. A lot of guys with AU I6's seem to be getting about 400-410Nm with a full exhaust, intake, cam and an edit, but at around 3500 rpm.

Have a go guys, surely the flaming won't be that bad....

have you takin into consideration the diff, some nice diff gears would make a big difference down the quarter, or are you just concentrating on the engine atm? is it manual or auto

a turbo

In the grand scheme of things, yes I have. For the record, 3.73 gears are on the cards eventually. However, that will probably require an increase on the 5700rpm limiter.

The purpose of this thread is to discuss what is involved in getting a decent torque increase.

if you get some serious head work anythings possible but thats alot more power/totque than anyone else is getting

overbore the engine. 4.2l.. there abouts I think is about the max you can go.. thats absolute max. Pistons? some flat top pistons? aftermarket ECU. uprated fuel pump and regs, just to name a few bits.

The amount of headwork needs to be done will really depend on how much the engine revs out to. By my research, the AU XR head is good to about 5000rpm (360cfm) and really starts trailing off after then. My AFR curve from the dyno chart supports this. I think that all the headwork needs to do is clean up the short turn radius and other minor port reshaping. I'm curious as to why you say that anything is possible with serious head work.

Hmm, bottom end rebuild will be avoided if possible.... I don't like the idea of increasing the engine bore as rod/stroke ratio is already pretty low (hence, high load on cylinder walls) and thinning the piston wallswould make this worse.
That said, I've noticed there are a couple of guys on FM running overbored motors and I haven't seen any of them having any issues so far. What is the wall thickness on the standard motors anyway?

interesting thread... ill be interested to see the excel sheets that you created, might give us an idea on the work you've already done...

Just thinking out of the box here, considering the bore:stroke ratio of the 4L is extremely long. "Hypothetically" de-stroking the engine will allow it to rev alot easier and maybe hit 6000-6500 rpm. Just a thought..

My 4L made it to just under 4.2L.. still plenty of meat left. Made stupid amounts of torque at low rpm, and with the right head and cam that would continue all the way through the rev range.

Yeah, thats what I thought too originally. However, the stroke is not the issue. There are a number of falcon sixes that happily rev past 6000rpm. I do believe Hyena's motor goes to 7000. I've found that its the ports that prevent the motor revving out. CSA isn't too bad but the short turn isn't good at all.

As for the Excel sheets I'm working on. Here's some screenshots.
http://i146.photobucket.com/albums/r270/hot_xr6/Excel1.jpg
http://i146.photobucket.com/albums/r270/hot_xr6/Excel2.jpg
http://i146.photobucket.com/albums/r270/hot_xr6/Excel3.jpg
http://i146.photobucket.com/albums/r270/hot_xr6/Excel4.jpg

Basically, I'm investigating the airflow of the engine and investigating the effects of different power/torque curves and driveline combinations.


Can you send me your dyno chart Waggin? And tell me what your gear ratios and redline were at the time?