View Full Version : Advice needed - GTiR cams in N/A setup

08-04-2016, 12:52 AM
Hey guys, need some help with my build.

I've been doing a bit of research regarding using the GTiR cams in an N/A motor. From what I've gathered they will be quite good and aggressive but I need cam gears to create an overlap as the GTiR stock cams have zero overlap. Can any of the more technically blessed give me some advise on how many degrees I should be adjusting roughly so I can save some money on dyno time.

Am I right in only adjusting the exhaust cam and leaving the intake in stock position? This would make it about the same as stock DE cams. Or should I be adjusting the Intake cam also? Any advice here would be much appreciated.

Build Details:
Gtir Motor
High comp pistons
stock quad throttles (but possibly ported, waiting for a price)
Custom plenum top, with 3.5 inch inlet
Standalone ECU
Fujitsubo exhaust manifold
3inch straight through exhaust

08-04-2016, 07:32 AM
what are you trying to achieve using a gtir head/block as a n/a motor?

08-04-2016, 01:10 PM
Not sure I understand your question? If you mean power, I don't know as there isn't much info to go by. Only one I found was from a guy in the u.s. that made 227whp from a similar build - back in 2008. Differences were aftermarket cams and a single throttle body intake manifold. I will be running E85 also, so if I get anywhere near that kind of figure I'll be happy.

Any info on the cams please?

09-04-2016, 01:16 AM
Stock GTI-R DET:
INTAKE - .394" (10.0) LIFT / 248 DUR - EXHAUST - .394" (10.0) LIFT / 248 DUR - OVERLAP - --

you want to make a n/a car make 170kw with those cams?

maybe with 10lbs of boost.

not sure if serious?

09-04-2016, 03:50 AM
No I doubt I'll get anywhere near that figure, especially with stock cams. Besides, US dyno's read higher. So realistically if I hit 180whp it would be nice. What are your thoughts? I dont know anyone else who has an N/A GTiR, and the heads do flow very well.

Edit: I just found a build from 2012 with dyno with the same setup 195whp! He added Tomei cams - 215whp

As for cams, I want to use the stock ones for now, this is a budget build using only spare parts that I have lying around. I'm trying to spend the least amount of money possible. The only new stuff I bought are the SR16VE pistons and rings, and I might port the throttles, haven't decided yet, depends on the price. And to answer any other questions No I dont want turbo, I already own a highly modified turbo pulsar in my small collection of cars. No I dont want to spend any more money and buy a VE. And no I'm not crazy :cool:, I'm just building something that I've always wanted to do, just for kicks.

So as you can see from the specs above there is zero overlap, which isn't good for N/A. Can anyone give me some advice here? Or am I going to be blowing more money on the dyno working it out :(

09-04-2016, 03:21 PM

if you have gone to the expense of going standalone and raising the comp/balancing etc, why not then do some head work with some valve springs and put in some bigger cams (260-275 duration). bear in mind anything over 260 will give you a very lopey idle and potential stalling/driveability issues. then you may find the throttle bodies are too small for your n/a application (most are 50mm minimum) so maybe consider doing something like the above photo?

09-04-2016, 04:09 PM
That's actually a brilliant idea thanks! Never thought of just removing the throttles and adding 1 large one, but would need to go bigger than 90mm to have any affect. The stock gtir are 45mm, so combined they make up the same surface area as a 90mm single throttle.

And as for cams and head work.. I would love to. Trust me I really would, but like I said I really don't want to spend the money. Yes I have a standalone, but I didn't buy it for this. Everything that I have listed are spare parts that I have lying around. Other than the Pistons. I do all the work myself, and machining done for almost nothing.

So I'd like to stick to the GTiR cams. I know that Nismo used to offer the GTiR exhaust cam as a DE Nismo upgrade. Like I've been saying, I just need to work out what degrees to set them at.

09-04-2016, 05:21 PM
for n/a you wont need anything bigger than a stock de throttle body. 70mm for allmotor.

typically, SR's and VE's like to see about 100 deg IN and about 105 EX C/L. (very old quote there) most oem de cams will work best at 0.0. this may change for you but.

09-04-2016, 07:32 PM
70mm on a DE would be an upgrade, but I don't think you've got that right when looking at the GTiR head.

The 4 stock throttles are 45mm each. That's an area of 1590 each * 4 = 6360 total surface area.
A 90mm single throttle = 6361 total surface area.
If I were to put a 70mm throttle on there, it would actually be a restriction. The stock setup is already larger.

Cams: Yeah I was actually looking at specs of stock cams today and depending on the year / motor, the DE's run 8* overlap or 16* overlap.
I'll take all these details with me to my tuner this week and see what ideas he has to say... although I know he's just going to tell me to buy some cams ;)

09-04-2016, 10:36 PM
again, a turbo motors needs are very different to your current setup.a very successful ex-sr20 racer in america has a formula for n/a racing which is that the t/b should be double the size of diameter of the inlet manifold runners. that does not apply to your setup at all.

most allmotor de's and ve's dont need to run more than a 70mm t/b.period. there is a wallace racing calculator out there for it, should you want to check it out.

the only restriction with your motors breathing will be the apparent lack of size of your wallet. :p

11-04-2016, 11:22 PM
Haha my wallet isn't lacking in size, I'm just trying to keep from thinning it out :D But I've lost that battle today. I was told off, flamed and laughed at by a few close friends, so I've decided to buy cams... On a side note, I found more goodies going through all my mountains of SR bits in the garage - PPM H-Beam rods! So the stock rods are out and the ppm ones are in. Its a total weight saving of about 550 grams!

So any advise on drop in cams for a GTiR? I've found some Tomei ProCam 270 Degree 12.50mm Lift (Solid Lifter) for a good price. Any thoughts? Or can you recommend anything better?

12-04-2016, 07:34 AM
that size and lift will work at high rpm for sure, and will most probably require valve springs and retainers for the head. get ready for the "shake rattle & roll" at idle lol.

12-04-2016, 02:34 PM
Ok Im looking at Supertech, their springs listing says max lift 17mm, but their complete kit with springs and retainers says max lift 10.6mm?? wtf?? Do you know any local companies that sell quality kits?

Also found these guys: http://www.precisionshims.com.au/products/sr20 Make shims for all sorts of engines, including the GTiR.

12-04-2016, 08:51 PM
i'm no expert on gtir's at all, but bc list their bc0240 kit for both sr20ve and gtir. now i have that kit in my ve, with kelford cams that feature the same duration and more lift. so maybe check them out?

that place for the shims has been mentioned b4. i recommend getting the cams clearanced right.

Leroy Peterson
12-04-2016, 09:28 PM
The supertech springs my GTiR head had were a bit weird... different heights between inner and outer springs. not sure if thats normal for supertech. I went to BC and havent looked back.
Precision Shims are good to deal with, but keep in mind its an operation out of an old mans home. Balancing the shims is a bitch, rocker condition and wear will also play a part.

I havent compared the GTiR block and a standard FWD block, but I think it would be very difficult to run the ITB's on a non-GTiR block. Thats just from my experience with the way the IACV sits plus the vacuum/air unit, oil block/cooler, millions of coolant hoses. Its a mess under the ITBs and i dont recommend them at all tbh.

This is JUST the coolant lines. Air/vacuum lines and box go ontop of this


Im not sure if this is for daily duties or not, but big cams dont make driving the car on the street very fun. Lose all down low and have to rev it to get it anywhere, plus needing a fairly high idle to keep the motor going.
Sorry i dont mean to be a party pooper, just as long as you know what you're in for! :)

12-04-2016, 09:43 PM
Cheers for the advice about the springs Leroy. Can I ask what cams you were using?

As for the motor, I am actually running a 54C motor, not a 53J. It will be N/A, but its still a complete GTiR motor. Also, its actually not too difficult to put the GTiR ITB's on a DE. Ive seen it done. :cool:

Leroy Peterson
13-04-2016, 05:01 PM
Well if that's the case, go for it. Probably won't max out stock injectors or anything oem haha.

It had tomei procam 260 11mm lift, changed to JUN 270 11/12mm.
The tomei's got away without lightened retainers, but defs needed double springs.

I'm just thinking of all the vacc lines and other intake bits you won't be needing. Plus turbo coolant/oil to the block. Keep us posted (plus pics!) of how you go.