How much low end power loss from 1 7/8" headers?
03-19-2009, 04:51 PM
#1
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How much low end power loss from 1 7/8" headers? How much are you missing out on down low by having 1 7/8" vs. 1 3/4"?
Last edited by Marc '99T/A; 03-20-2009 at 05:53 AM.
03-19-2009, 11:10 PM
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It's not a myth...Low end loss will depend on the setup and displacement you're running.
BTW, where the .3 sec & 3mph gains over the stock manifolds, because a set up 1 3/4" LTs will do the same for an ls1....
BTW, where the .3 sec & 3mph gains over the stock manifolds, because a set up 1 3/4" LTs will do the same for an ls1....
03-21-2009, 01:15 PM
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It's not a total myth 
. Just because one guy did a test does not mean it should warrent out judging the principles of how an engine and exhaust work.
If you put a FAST 92 set up on a stock LS1 you will lose power and throttle response, especially in low RPMs.
Put a set of 235cc heads on an otherwise stock car, you will lose power and throttle response especially in low rpms.
Exhaust is not any different - too big can be doing more harm than good. The biggest reason is scaveging effect. The faster you can get the exhaust to move the better. Just like anything else, the exhaust needs to be set-up to the rest of the set up.
The biggest thing to consider is part throttle if your car will be driven on the street. You will more than likely lose throttle response and mpg overanything else.
However like SOCalSPD said, with a stalled automatic trans the idea changes because now you have less engine rpm you have to consider for when you're doing your set up
. Just because one guy did a test does not mean it should warrent out judging the principles of how an engine and exhaust work.If you put a FAST 92 set up on a stock LS1 you will lose power and throttle response, especially in low RPMs.
Put a set of 235cc heads on an otherwise stock car, you will lose power and throttle response especially in low rpms.
Exhaust is not any different - too big can be doing more harm than good. The biggest reason is scaveging effect. The faster you can get the exhaust to move the better. Just like anything else, the exhaust needs to be set-up to the rest of the set up.
The biggest thing to consider is part throttle if your car will be driven on the street. You will more than likely lose throttle response and mpg overanything else.
However like SOCalSPD said, with a stalled automatic trans the idea changes because now you have less engine rpm you have to consider for when you're doing your set up
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03-21-2009, 02:05 PM
#8
It's not a total myth . Just because one guy did a test does not mean it should warrent out judging the principles of how an engine and exhaust work.
If you put a FAST 92 set up on a stock LS1 you will lose power and throttle response, especially in low RPMs.
Put a set of 235cc heads on an otherwise stock car, you will lose power and throttle response especially in low rpms.
Exhaust is not any different - too big can be doing more harm than good. The biggest reason is scaveging effect. The faster you can get the exhaust to move the better. Just like anything else, the exhaust needs to be set-up to the rest of the set up.
The biggest thing to consider is part throttle if your car will be driven on the street. You will more than likely lose throttle response and mpg overanything else.
However like SOCalSPD said, with a stalled automatic trans the idea changes because now you have less engine rpm you have to consider for when you're doing your set up
. Just because one guy did a test does not mean it should warrent out judging the principles of how an engine and exhaust work.If you put a FAST 92 set up on a stock LS1 you will lose power and throttle response, especially in low RPMs.
Put a set of 235cc heads on an otherwise stock car, you will lose power and throttle response especially in low rpms.
Exhaust is not any different - too big can be doing more harm than good. The biggest reason is scaveging effect. The faster you can get the exhaust to move the better. Just like anything else, the exhaust needs to be set-up to the rest of the set up.
The biggest thing to consider is part throttle if your car will be driven on the street. You will more than likely lose throttle response and mpg overanything else.
However like SOCalSPD said, with a stalled automatic trans the idea changes because now you have less engine rpm you have to consider for when you're doing your set up
Sorry I should have added the test was on a stock engine, making it a total myth for ls1 based cars.
03-21-2009, 03:29 PM
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Yes, but what did you replace? Of course you are going to gain if you are replacing the stock manifolds and y-pipe.
You might even see gains with a quality 1 7/8 header over a budget 1 3/4. But you are comparing apples to oranges because I garrantee your gains were over the stock manifolds and not a set of 1 3/4.
You might even see gains with a quality 1 7/8 header over a budget 1 3/4. But you are comparing apples to oranges because I garrantee your gains were over the stock manifolds and not a set of 1 3/4.
03-21-2009, 04:02 PM
#10
Depends on the heads more than anything. Huge exhaust port with no velocity could probably use the smaller headers better. Small exhaust port without enough flow could use the 1-7/8". You select header primary exhaust diameter in accordance with head flow, period, because it is a tuned system. The collector length becomes the next critical piece for optimizing the powerband, but I don't see that much in the LS-world.
On a stock car, the 1-7/8" will act as a more efficient crutch than the 1-3/4", thus delivering slightly better performance. But once aftermarket/ported heads are in the mix or cams, they can help the exhaust side of the engine. Then it becomes a combo issue.
On a stock car, the 1-7/8" will act as a more efficient crutch than the 1-3/4", thus delivering slightly better performance. But once aftermarket/ported heads are in the mix or cams, they can help the exhaust side of the engine. Then it becomes a combo issue.
03-21-2009, 04:29 PM
#11
It's not a total myth . Just because one guy did a test does not mean it should warrent out judging the principles of how an engine and exhaust work.
If you put a FAST 92 set up on a stock LS1 you will lose power and throttle response, especially in low RPMs.
Put a set of 235cc heads on an otherwise stock car, you will lose power and throttle response especially in low rpms.
Exhaust is not any different - too big can be doing more harm than good. The biggest reason is scaveging effect. The faster you can get the exhaust to move the better. Just like anything else, the exhaust needs to be set-up to the rest of the set up.
The biggest thing to consider is part throttle if your car will be driven on the street. You will more than likely lose throttle response and mpg overanything else.
However like SOCalSPD said, with a stalled automatic trans the idea changes because now you have less engine rpm you have to consider for when you're doing your set up
. Just because one guy did a test does not mean it should warrent out judging the principles of how an engine and exhaust work.If you put a FAST 92 set up on a stock LS1 you will lose power and throttle response, especially in low RPMs.
Put a set of 235cc heads on an otherwise stock car, you will lose power and throttle response especially in low rpms.
Exhaust is not any different - too big can be doing more harm than good. The biggest reason is scaveging effect. The faster you can get the exhaust to move the better. Just like anything else, the exhaust needs to be set-up to the rest of the set up.
The biggest thing to consider is part throttle if your car will be driven on the street. You will more than likely lose throttle response and mpg overanything else.
However like SOCalSPD said, with a stalled automatic trans the idea changes because now you have less engine rpm you have to consider for when you're doing your set up
Man...you have absolutely no idea what you are talking about. I can tell you have no dyno experience or knowledge on any facts you are discussing other than what you have read on the internet.
1) Fast 90/90 setup picks up good gains from 2500+ rpm up. I have tested multiple cars back to back on the dyno with stock internal LS1's. Any statement to the contrary, is well, wrong.
2) I would like to see you put your most 235cc aftermarket casting on a 3.900" ls1 bore, most 235cc casting heads larger valves will not clear a 3.9" bore. Also most 235+cc aftermarket castings are a bad choice on a small cube motor. Standard AFR/TFS 225's dont show gains over a 205/215 offering on a stock cube motor. I would only use a small bore AFR 225 on a FI setup.
3) You will not lose throttle response or fuel mileage with a larger header. You have no 1st person real world experience testing these things.
I would highly recommend no one take advice from this person in anyway related to ANY subject. Believing whats written on the internet causes sooo much misinformation is rediculous.
Last edited by SoCalSpd; 03-22-2009 at 07:29 PM.
03-21-2009, 08:49 PM
#12
Yes, but what did you replace? Of course you are going to gain if you are replacing the stock manifolds and y-pipe.
You might even see gains with a quality 1 7/8 header over a budget 1 3/4. But you are comparing apples to oranges because I garrantee your gains were over the stock manifolds and not a set of 1 3/4.
You might even see gains with a quality 1 7/8 header over a budget 1 3/4. But you are comparing apples to oranges because I garrantee your gains were over the stock manifolds and not a set of 1 3/4.
