346ci FI vs 408ci FI
04-26-2007, 09:56 AM
#121
Originally Posted by bboyferal
/thread
This information answers all our questions...
Build a 408+ ... Easy. Sure. But putting a turbo that justifies it? Most people don't... From there we arrive at the advice to go smaller on the engine.
Hell, if a small frame 88 is IDEAL in racing trim for less than 370 cid, then many people on this site have it all wrong.
Going smaller motor with the kind of turbos we typically run makes more sense to me than big time hacking or running the wrong turbos. On LS1 F-body's we have only so much room.
Cablebandit is joking 1.5L would be ideal, but what's funny is that if your turbo size were limited to T-67's (Like some LS1's here run) and such, that would actually be a good idea... It doesn't make any sense to run motors that push turbos into inefficiency. Now, if I could fit two T-76's in my engine bay, I might run a 427 of course. But I won't... It's a street car like many of us have, so the fact is we are limited in this way... And going bigger cubes to make power that way doesn't solve the problem, it just makes the turbo less efficient unless you can run enough turbo to keep the proportion between turbo and motor optimal.
This information answers all our questions...
Build a 408+ ... Easy. Sure. But putting a turbo that justifies it? Most people don't... From there we arrive at the advice to go smaller on the engine.
Hell, if a small frame 88 is IDEAL in racing trim for less than 370 cid, then many people on this site have it all wrong.
Going smaller motor with the kind of turbos we typically run makes more sense to me than big time hacking or running the wrong turbos. On LS1 F-body's we have only so much room.
Cablebandit is joking 1.5L would be ideal, but what's funny is that if your turbo size were limited to T-67's (Like some LS1's here run) and such, that would actually be a good idea... It doesn't make any sense to run motors that push turbos into inefficiency. Now, if I could fit two T-76's in my engine bay, I might run a 427 of course. But I won't... It's a street car like many of us have, so the fact is we are limited in this way... And going bigger cubes to make power that way doesn't solve the problem, it just makes the turbo less efficient unless you can run enough turbo to keep the proportion between turbo and motor optimal.
But as a said before with a heavy car a bigger engine and mid sized turbo may not be optimal for maximum power production, but it would be more fun drive, especially off boost.
I surely understand how and why my incons made more power on my 346 than my 408. With no space or turbo limitations, more cubes means more overall power
04-26-2007, 12:12 PM
#123
Jose why do you keep talking about a t76? are you running a special on these or what? The original post doesnt say he is limited to a t76...just a streetcar and which cubes are better.
I have had both 346/408 in a street car....the bigger cubes are much more enjoyable to drive off boost. Now if you are talking mostly track car, KP has shown that small cubes can get the job done. When you first go from a stock motor to a low compression 346 forged motor for boost, there is a noticeable difference in power down low when driving on the street. Big cubes more than make up for that but you have to decide if its worth the extra money...everybody has different tolerances.
I have had both 346/408 in a street car....the bigger cubes are much more enjoyable to drive off boost. Now if you are talking mostly track car, KP has shown that small cubes can get the job done. When you first go from a stock motor to a low compression 346 forged motor for boost, there is a noticeable difference in power down low when driving on the street. Big cubes more than make up for that but you have to decide if its worth the extra money...everybody has different tolerances.
04-26-2007, 12:15 PM
#124
Originally Posted by cablebandit
Jose why do you keep talking about a t76? are you running a special on these or what? The original post doesnt say he is limited to a t76...just a streetcar and which cubes are better.
I have had both 346/408 in a street car....the bigger cubes are much more enjoyable to drive off boost. Now if you are talking mostly track car, KP has shown that small cubes can get the job done. When you first go from a stock motor to a low compression 346 forged motor for boost, there is a noticeable difference in power down low when driving on the street. Big cubes more than make up for that but you have to decide if its worth the extra money...everybody has different tolerances.
I have had both 346/408 in a street car....the bigger cubes are much more enjoyable to drive off boost. Now if you are talking mostly track car, KP has shown that small cubes can get the job done. When you first go from a stock motor to a low compression 346 forged motor for boost, there is a noticeable difference in power down low when driving on the street. Big cubes more than make up for that but you have to decide if its worth the extra money...everybody has different tolerances.
That's cause 95% of the kits are T4 based and T76 is the MOST popular choice.
04-26-2007, 12:33 PM
#125
You don't have to lower the compression to much just because you are gonna boost it. I am having my 348 short built with 9.8:1 compression and still am running 12 lbs of boost on the street with pump. Power down low won't be hit bad at all, and it will still run like a raped ape on the boost.
04-26-2007, 12:50 PM
#126
Registered User
Join Date: Jun 2002
Location: Forced Induction Heaven
Posts: 453
Likes: 0
Received 0 Likes
on
0 Posts
Originally Posted by VINCE
What I have learned out of reading this entire thing is I should have sold my crank and ran with a 370ci.. LOL!!
Its ironic that you mention this as it was my biggest decision...that being whether or not to rebuild my 346/7 cid or do an LS2 364-370 cid. I like the short stroke 3.622 and more bore with Turbo setups. At no time did I consider doing a 388+ cid motor.
If I was running a blower still I probably would have went to a 370cid to make up for a little bit of the tq loss at low rpm from parasitic loss from driving the blower...but even then I look back to when I had my D1 on my 346cid and it was incredible to drive....so parasitic loss is probably all just in my head from reading these boards.
A large part of the decision making process...was having to do the complete change over from LS6 to LS2 for very little benefit IMO. I know that there is a variety of change over kits that help relocating things easier but you still have to buy all of it..and for what???...a little more tq in the lower rpm band...don't need it below 3K rpms....in the end I would have to get a re-tune as well. It was just hard to justify when my car ran perfect with a 346cid and made a **** load of power...plus never any overheating issues and great fuel economy.
If I was going to run a 427cid it would probably be NA..with a 100 shot located somewhere for extra fun through 4th gear.
Originally Posted by cablebandit
I have had both 346/408 in a street car....the bigger cubes are much more enjoyable to drive off boost. Now if you are talking mostly track car, KP has shown that small cubes can get the job done. When you first go from a stock motor to a low compression 346 forged motor for boost, there is a noticeable difference in power down low when driving on the street. Big cubes more than make up for that but you have to decide if its worth the extra money...everybody has different tolerances.
At 8.97:1 my tach would swing just as quick to 3K rpms (low boost threshold) as I remember when it was 9.7:1. If it in fact does swing a little slower in 1st-2nd to 3K rpms..then I am happy about it. But I just refreshed my motor and as a result of resurfacing the heads and a slightly smaller hg...my static CR is now 9.2:1. So I will report any difference that I feel with a slightly increased CR.
Last edited by Shinobi'sZ; 04-26-2007 at 12:59 PM.
04-26-2007, 03:28 PM
#127
Dr Turbo, you mean the stenod...ofi...aps...Streettuna...tti race kits?
My drop in compression was noticeable for sure...especially with a tight stall. Quicksilverado had the same experience with his. I guess everybody has a differently calibrated butt dyno
Next we will all be running the supra motor!!
My drop in compression was noticeable for sure...especially with a tight stall. Quicksilverado had the same experience with his. I guess everybody has a differently calibrated butt dyno
Next we will all be running the supra motor!!
Last edited by cablebandit; 04-26-2007 at 03:33 PM.
04-26-2007, 06:14 PM
#128
Staging Lane
Join Date: Dec 2006
Location: St. Louis, MO
Posts: 54
Likes: 0
Received 0 Likes
on
0 Posts
Wow you guys have me so confused so is it a matter of picking the turbo and then building the motor?
Also how do you figure out what you need to spool a turbo?
Also how do you figure out what you need to spool a turbo?
04-26-2007, 06:35 PM
#130
TECH Junkie
iTrader: (9)
Join Date: Apr 2005
Location: Miami, FL
Posts: 3,472
Likes: 0
Received 0 Likes
on
0 Posts
Originally Posted by cablebandit
Dr Turbo, you mean the stenod...ofi...aps...Streettuna...tti race kits?
My drop in compression was noticeable for sure...especially with a tight stall. Quicksilverado had the same experience with his. I guess everybody has a differently calibrated butt dyno
Next we will all be running the supra motor!!
My drop in compression was noticeable for sure...especially with a tight stall. Quicksilverado had the same experience with his. I guess everybody has a differently calibrated butt dyno
Next we will all be running the supra motor!!
But of course, we must have our street cars... So let's just handicap the turbo instead...
I'm not gonna be guilty of that, so I'll just stick with a 346 thank you cuz I'm stuck with a 76 trim.
... But that's just me, of course... Many more options now.
04-26-2007, 06:41 PM
#132
TECH Junkie
iTrader: (9)
Join Date: Apr 2005
Location: Miami, FL
Posts: 3,472
Likes: 0
Received 0 Likes
on
0 Posts
Originally Posted by Kuhnstyle86
Im so lost Ive been reading on turbo setups for the past week and im just so lost lol.
04-26-2007, 06:45 PM
#134
Originally Posted by Kuhnstyle86
Im so lost Ive been reading on turbo setups for the past week and im just so lost lol.
Ask the guys who design them and you won't be. Jose is the man when it comes to turbos...plain and simple.
04-26-2007, 06:46 PM
#135
Originally Posted by 52172
No its a matter of picking the rwhp desired and going from there.
1. rwhp desired
2. Turbo to reach your desired goal and space contraints
3. The engine that will most effectively utilize this turbo
04-26-2007, 06:49 PM
#136
TECH Junkie
iTrader: (9)
Join Date: Apr 2005
Location: Miami, FL
Posts: 3,472
Likes: 0
Received 0 Likes
on
0 Posts
Originally Posted by DrTurbo
Correct the list as was posted in the earlier posts should be:
1. rwhp desired
2. Turbo to reach your desired goal and space contraints
3. The engine that will most effectively utilize this turbo
1. rwhp desired
2. Turbo to reach your desired goal and space contraints
3. The engine that will most effectively utilize this turbo
04-26-2007, 06:51 PM
#139
Originally Posted by bboyferal
This makes sense to the performance enthusiast but sadly might not be popular because many LS1 owners gotta have "cubes" and "more torque than a meager 346" and whatnot.
04-26-2007, 06:53 PM
#140
Staging Lane
Join Date: Dec 2006
Location: St. Louis, MO
Posts: 54
Likes: 0
Received 0 Likes
on
0 Posts
so say i were to want between 850 - 900 rwhp I would go with a turbo making 1200-1400 so I can make up for what i will lose drivetrain.
like I was looking at an S85
like I was looking at an S85