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1g hx35 stock block (6 bolt) w/2g head

636chris

Proven Member
153
0
Aug 15, 2009
philadelphia, Pennsylvania
whats up guys . i was wondering if i run a 2g head on my six bolt with my 7 blade hx35 ,what type of spool i would be looking at with stock cams ,stock intake manifold , with a tubular t3 exhaust manifold in the stock housing? what about different cams like k272's. does anyone have a similar set up. ill be tuning on jackal sd or link not too sure yet. hoping to put the car together in the next few weeks . im currently in machine shop now in school so i may do some porting but lets leave that out of the equation
 

JusMX141

Moderator
15,120
1,188
Dec 13, 2005
Greensburg, Pennsylvania
The chance that you're going to find someone with your exact setup who can give you an idea of spool is slim to none; not to mention two identical setups can have varying spool simply by changing the tune. That in mind, guessing spool is as pointless as guessing horsepower.
 

636chris

Proven Member
153
0
Aug 15, 2009
philadelphia, Pennsylvania
I get what your saying but hypithectically speaking wouldn't the bump in compression with the 2g head give slightly better spool , if everything else Falls in order . Example the tune
 

636chris

Proven Member
153
0
Aug 15, 2009
philadelphia, Pennsylvania
Any gain or loss in compression can influence spool times
 

narf

Probationary Member
25
0
Apr 15, 2005
vernon, Connecticut
Ive got a 6bolt bottom, 2g head, 272s, hx 35 7blade and love it. Zero port work feels like a b16g response wise but after 5k its a whole diffrent beast. Thats the bolt on housing btw... You will have no regrets with the 2g head.... Dont port it !!!
Proper oil feed and drain helped massively as far as spool is concerned. I saw about a 200rpm change reducing my feed restrictor to.066 from the .078 recomended. Pressure is low limit of holsets recomendations.
 

636chris

Proven Member
153
0
Aug 15, 2009
philadelphia, Pennsylvania
Thanks for the response. Exactly what I was looking for. Do you have balence shafts ? Also what size is you feed and drain. Right now ill have a six bolt bottom end,2g head with arps , oem composite gasket. I'm keeping the balence shafts as of now, which may change because my motor is out. Ill be using 90 turbo cams until I can afford dk272's or dk274's.
 

narf

Probationary Member
25
0
Apr 15, 2005
vernon, Connecticut
No bs. -4 reduced to.066 feed -12 return. The head means almost nothing compression wise... I chose it for the difference in volumetric efficiency. Much more responsive off/building boost
 

636chris

Proven Member
153
0
Aug 15, 2009
philadelphia, Pennsylvania
Ok cool that's what I was looking for . My set up is similar only I'm running an open t3 housing unless a deal pops up on a bep but not likely due to ill be needing a new exhaust and downpipe set up going bolt on
 

T is for TURBO

Proven Member
2,251
20
Jan 15, 2005
Milwaukee, Wisconsin
Any gain or loss in compression can influence spool times

I'm not disagreeing. But I think the CR ratio affect on spool is negligible between 1g and 2g heads. Most of your increased spool characteristics are going to come from the better flow design of the 2g intake and exhaust ports.
 

636chris

Proven Member
153
0
Aug 15, 2009
philadelphia, Pennsylvania
i ment open t3 manifold w/stock 8 blade hx35 housing . to add to my above post
 

donniekak

DSM Wiseman
5,623
973
Mar 23, 2008
Surprise, Arizona
Compression doesnt have much effect on spool. I've run the same setup on 7.8:1, 8.3:1, and 9:1. Actual logs show about the same psi, at the same rpm. Actually, the 8.3:1 setup spools fastest because of a better tune.
What happens with higher compression is that the engine will go from no boost to full boost in a faster time, but the rpm that boost comes on is the same. This is possible because the higher compression engine makes more off boost power, and more power at the same boost.


So, a 3000-5000 rpm pull on a high compression engine may take 3 seconds, and full boost occurs at 4200 rpms. Now on a lower compression engine of the same displacement the same pull may take 3.5 seconds, and still reach full boost at 4200 rpms. Spool is unchanged, but perception of spool is changed by making more power.
 

LandSpeed-DSM

Proven Member
2,546
77
Dec 5, 2011
Chicago, Illinois
Compression doesnt have much effect on spool. I've run the same setup on 7.8:1, 8.3:1, and 9:1. Actual logs show about the same psi, at the same rpm. Actually, the 8.3:1 setup spools fastest because of a better tune.
What happens with higher compression is that the engine will go from no boost to full boost in a faster time, but the rpm that boost comes on is the same. This is possible because the higher compression engine makes more off boost power, and more power at the same boost.


So, a 3000-5000 rpm pull on a high compression engine may take 3 seconds, and full boost occurs at 4200 rpms. Now on a lower compression engine of the same displacement the same pull may take 3.5 seconds, and still reach full boost at 4200 rpms. Spool is unchanged, but perception of spool is changed by making more power.

Correct.

Higher compression actually wastes less heat/energy into the exhaust gas to light the turbine with.

But because it creates more torque, you reach the rpm of your boost threshold faster, and can make that negligible.

I had no more problems spooling mid frame turbos on a tired 120k mile 7.8:1 bottom end then I did on any of the motors since then.
 
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