Getting back some low end power
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Getting back some low end power Ever since I installed my HP header/test pipe I noticed that I lost a lot of low end power. So I started thinking about the good old days when I raced quads and rememberd that we always welded a reducer into large aftermarket head pipes to make a little back pressure.
Theese reducers were called "tourque stuffers" since stuffing them into the header added tourque. So Im thinnking about machining some reducers for my cars header, but Im not shure If I should just make one to put between the header and test pipe. Or 4 to put into the primarys.
Theese reducers were called "tourque stuffers" since stuffing them into the header added tourque. So Im thinnking about machining some reducers for my cars header, but Im not shure If I should just make one to put between the header and test pipe. Or 4 to put into the primarys.
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Rep Power: 330 I figure I'll measure the I.D. of the primarys on the stock header and then measure the I.D. of the hp header and split the difference w/ the reducers, that way I should get back some low end, and still have more top end over stock.
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Rep Power: 0 Originally posted by RiceBuRNeR
I figure I'll measure the I.D. of the primarys on the stock header and then measure the I.D. of the hp header and split the difference w/ the reducers, that way I should get back some low end, and still have more top end over stock.
I figure I'll measure the I.D. of the primarys on the stock header and then measure the I.D. of the hp header and split the difference w/ the reducers, that way I should get back some low end, and still have more top end over stock.
Oh, I think I understand now....I'm talk to my friend about this a little more because it makes more sense to me now....Maybe he can help me with the work....Thanks for the idea Rice. Keep us informed on what you come up with
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Rep Power: 0 This is a "black art" It has to do w/ Note2. GO for it, if you wanna experiment. We would love to see some results!
From another post of mine:
u shouldn't need more than 2- 2.25" piping. Remember the important thing is exhaust escape velocity, that is why bigger is always not better. The better companies (& i'm expecting to get flamed, already..) like DC sports have sligthly bigger piping for their headers/ piping. This concurs w/ greatcasa's post that the stock piping is a good size. Most of the restriction comes from 3 areas:
the CAT
the Muffler
the pre- silencer?
So you will get maximum gains from changing these & just having mandrel bends in your piping. Now all of the above applies for an NA car of mild tune (less than 200 hp at the crank)
If you run nitrous/ forced induction & get over 200 hp at the crank, you will need a different exhaust set- up. Here's my opinion on this:
As exhaust velocity is the key (& if you do your research, this will be validated) it may be better to have a custom header/ piping such that you have 2 exhaust pipes/ CATS/ Muffllers (as w/ narrower piping you have higher exhaust velocities)
Note1: in the above i haven't mentioned backpressure at all- for a reason; it complicates matters. Smaller piping will introduce more backpressure, which will rob the engines ability to empty the cyliders of waste gasses, hence retaining more heat & waste gasses, which means less oxygen in the cylinder for combustion. So this is really a "black art" where you want to balance backpressure/ ehaust velocity.
Note 2: Then there are also pressure waves that can be used to aid filling/ emptying out the cylinders (from pressure waves bouncing off the piping, where there is a change in gas- flow ex. where the 4 pipes converge into 1 in a 4-1 header)
Note 3: Then there is also intake & exhaust matching. You want to design your exhaust to match your intake i.e. the ability of your engine to evacuate air should match the ability of your engine to intake air (because if your intake flows much more air than exhaust, you won't be efficiently emptying out the cylinders each combustion cycle)
Any questions?
From another post of mine:
u shouldn't need more than 2- 2.25" piping. Remember the important thing is exhaust escape velocity, that is why bigger is always not better. The better companies (& i'm expecting to get flamed, already..) like DC sports have sligthly bigger piping for their headers/ piping. This concurs w/ greatcasa's post that the stock piping is a good size. Most of the restriction comes from 3 areas:
the CAT
the Muffler
the pre- silencer?
So you will get maximum gains from changing these & just having mandrel bends in your piping. Now all of the above applies for an NA car of mild tune (less than 200 hp at the crank)
If you run nitrous/ forced induction & get over 200 hp at the crank, you will need a different exhaust set- up. Here's my opinion on this:
As exhaust velocity is the key (& if you do your research, this will be validated) it may be better to have a custom header/ piping such that you have 2 exhaust pipes/ CATS/ Muffllers (as w/ narrower piping you have higher exhaust velocities)
Note1: in the above i haven't mentioned backpressure at all- for a reason; it complicates matters. Smaller piping will introduce more backpressure, which will rob the engines ability to empty the cyliders of waste gasses, hence retaining more heat & waste gasses, which means less oxygen in the cylinder for combustion. So this is really a "black art" where you want to balance backpressure/ ehaust velocity.
Note 2: Then there are also pressure waves that can be used to aid filling/ emptying out the cylinders (from pressure waves bouncing off the piping, where there is a change in gas- flow ex. where the 4 pipes converge into 1 in a 4-1 header)
Note 3: Then there is also intake & exhaust matching. You want to design your exhaust to match your intake i.e. the ability of your engine to evacuate air should match the ability of your engine to intake air (because if your intake flows much more air than exhaust, you won't be efficiently emptying out the cylinders each combustion cycle)
Any questions?
DaK is right. 4 cycle engines dont need backpressure. It's about exit speed. A larger pipe doesnt mean higher exit speeds. It means more volume is able to pass through. But ideally you want to meet in the middle. As much volume as possible going as fast as it can. Back pressure is needed in 2 stroke engines due to scavenging. I think people put 4 inch pipes on thier honda..then when they had no low end power the just assumed "honda's must need backpressure." I would go intot he physics of all this but it would take waaay to much typing. Just do a search online for volume vs. speed or volume vs. velocity.
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