Garrett Gt35r Install
02-08-2008 | 11:23 AM
#121
Nordschleife Master
Joined: Aug 2001
Posts: 5,552
Likes: 18
From: Stockholm, Sweden
I don't know. We're talking a well built 3.0 liter here. If you have a good 4000 rpm powerband is it really always better with shorter gearing?
My guess is that with a powerful enough engine (with wide powerband) you're better off accelerating instead of wasting time slowing down during extra shifts.
My guess is that with a powerful enough engine (with wide powerband) you're better off accelerating instead of wasting time slowing down during extra shifts.
02-08-2008 | 12:52 PM
#122
Rennlist Member
Joined: Feb 2006
Posts: 18,926
Likes: 99
From: Australia
Well my guess is that you're all correct in a sense. I found for the short times I have had the S2 gearing on the track it was better in more ways than it was worse and as Chris says it really depends on the track. We don't race on many long tracks here and the stock 5 speed gearing was a little too oriented to fast autobahn cruising. With the shorter gearing you tend to find your in a better part of the powerband in general, however it's not 100% perfect, there are some corners now where it's either a bit short or just too long. Obviously a custom 'box with perfect gearsets would be ideal. We're looking into a few options for the future. On the street you do shift a bit more which I really enjoy as I see gearshifting as a bit of a dying art but on the longer hwy cruises, you do feel like you need an overdrive to be sure. We will definitely need something more suited to Bathurst if we can make it there this year!
02-08-2008 | 05:21 PM
#123
Drifting
Joined: May 2006
Posts: 3,481
Likes: 0
From: Melbourne
running 18" or the 17" mostly with the s2 gearing? have you calculated the difference from a taller rear tyre? its a convenient way to make a small gearing adjustment since you have both sets of rims
02-08-2008 | 07:27 PM
#124
Rennlist Member
Joined: Feb 2006
Posts: 18,926
Likes: 99
From: Australia
Well it's possible but mostly the OD of tyres available are of similar sizes. Besides for now the gearbox is what it is and I do think it's a good mod. Perhaps with a bunch more hp and capacity it might be too short. We'll have to see....soon...
02-08-2008 | 10:37 PM
#125
Banned
Joined: Jun 2001
Posts: 1,635
Likes: 0
From: San Diego
Just thought I'd do a quick update. Over this weekend I messed around with the 35r setup to see where there might be any fitment issues, considering I am using the 4" T04S compressor housing. Sorry I don't have any pics. I might be able to get some next weekend if anyone really wants me to. Here's the bad news, GT series turbos with the 4" T04S housing and with the SFR setup (modified center section and a ~6mm spacer for the turbo mount) will NOT fit without doing an AC delete. Keep in mind, I am talking about "perfect" fitment which would entail being able to run a 3-4" intake pipe without any hassles. An AC delete would position the alternator far enough out of the way that there wouldn't be any issue. Now, if someone doesn't mind a less than optimal and compromised setup (and they want to retain the AC), there is just enough room that you could still run the 4" housing, remove the plastic cover from the back of the alternator, and run a reducer coupler probably around a 4" to 3" or smaller however IMO this defeats the purpose of the 4" housing and is counterproductive for my purpose (high hp, improved top-end flow, etc). The T04E 3" housing would fit quite a bit better and would have barely any fitment issue (might be necessary to use a slight reducer coupler), even with the alternator in the stock position. Personally, in my experience the larger T04S compressor housing is really not going to be necessary to use except for those that are going for big power.
For my specific setup, I've figured out the easiest way to retain the A/C but I have a custom short runner intake that frees up quite a bit of room around the turbo, so my example is probably not going to work for everyone. With my setup, I am probably going to have a ~ 3/4" or 1" spacer machined for the mount to use instead of the SFR spacer. This will position the turbo up high enough to clear the alternator, and then it will only be necessary to add 1" the top of the cat pipe so that it will still reach the downpipe. However, I still need to test this method with the stock intake manifold to see if this will cause any fitment issues on that side. I have a sneaking suspicion that the turbo would sit too high for the intake to fit. Although I've figured out what will work for my setup, I am still going to examine what is necessary to make this setup fit with the stock intake and without doing an a/c delete for those that are considering a similar setup but want to retain most of the stock components. At this point it looks like a reducer and removing the alternator shroud should be enough to get the job done. In the next few weeks I'll do some more work with this and post updates with pics to further illustrate what I'm talking about. Ultimately, I'd recommend that for those considering making less than say 450-500+whp, just bypass these issues entirely and use the 3" T04E housing. The T04S will really just be more trouble than it's worth for anything except a high hp setup. Also, for anything over 400whp I would highly recommend going with a .82a/r exhaust housing (assuming the SFR setup, in a KKK a #10 would be similar sized). Although spool will come in a few hundred rpm later than with a .63a/r, at those boost/power levels the turbo would be significantly more efficient with a .82 which IMO would be preferrable to a few hundred rpm sooner spool.
For my specific setup, I've figured out the easiest way to retain the A/C but I have a custom short runner intake that frees up quite a bit of room around the turbo, so my example is probably not going to work for everyone. With my setup, I am probably going to have a ~ 3/4" or 1" spacer machined for the mount to use instead of the SFR spacer. This will position the turbo up high enough to clear the alternator, and then it will only be necessary to add 1" the top of the cat pipe so that it will still reach the downpipe. However, I still need to test this method with the stock intake manifold to see if this will cause any fitment issues on that side. I have a sneaking suspicion that the turbo would sit too high for the intake to fit. Although I've figured out what will work for my setup, I am still going to examine what is necessary to make this setup fit with the stock intake and without doing an a/c delete for those that are considering a similar setup but want to retain most of the stock components. At this point it looks like a reducer and removing the alternator shroud should be enough to get the job done. In the next few weeks I'll do some more work with this and post updates with pics to further illustrate what I'm talking about. Ultimately, I'd recommend that for those considering making less than say 450-500+whp, just bypass these issues entirely and use the 3" T04E housing. The T04S will really just be more trouble than it's worth for anything except a high hp setup. Also, for anything over 400whp I would highly recommend going with a .82a/r exhaust housing (assuming the SFR setup, in a KKK a #10 would be similar sized). Although spool will come in a few hundred rpm later than with a .63a/r, at those boost/power levels the turbo would be significantly more efficient with a .82 which IMO would be preferrable to a few hundred rpm sooner spool.
We have a smaller alternator set-up which will allow you to use a 4" intake pipe and retain your a/c.
Tim
02-09-2008 | 05:33 PM
#127
Banned
Joined: Jun 2001
Posts: 1,635
Likes: 0
From: San Diego
02-10-2008 | 11:08 AM
#130
Drifting
Joined: Jan 2004
Posts: 2,023
Likes: 0
From: Michigan
02-10-2008 | 03:41 PM
#131
Rennlist Member
Joined: Feb 2006
Posts: 18,926
Likes: 99
From: Australia
Thanks Stephan. That was a great post. Have you had trouble free motoring since? Also I read that you're going to modify your car further to do some serious boost runs. What turbo are you planning to use for this?
02-10-2008 | 09:33 PM
#132
Drifting
Joined: Jan 2004
Posts: 2,023
Likes: 0
From: Michigan
I initially picked a GT45R but going over the compressor maps this may not be the right one. It depends what intake I end up with. Boost will be set at 35psi or so then I have a momentary thumb button on my steering wheel that will switch me to 40-45psi. For the past 3 years I ran at 23psi normally and switched boost at 27psi without any ill effects(xylene helps). I love the switched boost, it feels like nitrous with a bottle that never empties.
Aside from the turbo, before turning up the boost any more I need to find a BoV, throttle body, and wastegate that won't leak like the current ones I have do. lol
02-10-2008 | 09:43 PM
#133
Rennlist Member
Joined: Feb 2003
Posts: 9,732
Likes: 22
From: NJ
Thanks for the good work.
Raj
02-10-2008 | 09:57 PM
#135
Drifting
Joined: Jan 2004
Posts: 2,023
Likes: 0
From: Michigan
I know spiking high boost and a constant high boost are different but that's why I will have the 45psi only on momentary switch.