16G Set-up Questions

[turbowop]

Quoting crankwalk:
^Saying they are mandatory (which they aren't) and then never using them for their purpose is definitely something I see DSM people doing more than other folks.



While not absolutely mandatory, how are people that have them not using them to their potential? The whole point of having one is to keep fuel pressure set to a level that allows for a linear boost/fuel pressure increase. If people want to set their base fuel pressure to stock levels while using a high flow fuel pump, they're using the thing for a reason. Those that choose to tune around a non-linear fuel curve are free to do so, but using proper tools/tuning techniques to acquire the best possible power/driveability/economy is certainly not a fad. There is no argument that max power can't be made with the stock FPR, but it forces you to compromise on economy and driveability.

 

Just to go off topic on fpr's I have a 1g auto turbo fpr which bumps up the base pressure and I have a Bosch 044, how does having a stock fpr on a bigger pump compromise driveabilty or economy? The car has a dyno tune/chip/safc and gets 25 mpg and drives like a stock car. Big retarded pumps on a stock fpr with no tuning would cause overrun issues but I would hope people don't do that stuff still anyway.

 

[Muskrat]

Quoting Polish:
Quoting CutlassJim:
A single 2.5" exhaust pipe is good for around 50 lbs/min of airflow through an engine. 3" exhausts are just a DSM fad where ZOMG I need a 3" exhaust.

/rant



2.5 *will* flow enough to make that power, perhaps.

BUT 3" would make more. Guaranteed.

Someone in the Midwest had a Apex'i or similar type muffler (That necks down to 2.5" inside) on their car and were making around 450whp or so on the dyno. They cut *JUST* the muffler off on the dyno and the car picked up around 50whp. I forget who it was but the car was sold long ago and has been for sale a time or two since then. But to me that is more than enough proof. You can believe what you want.



Actually, based on my calculations your numbers line up with what I said above.

In order to make 450 hp (brake horsepower, not wheel hp. So he was actually making more at the crank) you need to be flowing about 52 lb/min of air through the engine. So if his setup was actually capable of over 500 bhp then yes, his exhaust was a restriction, and opening it up let it breath. a full 3" set-up (or perhaps larger) was appropriate in this case.

However, if your setup can't outflow your exhaust, there's no need to go bigger. Based on CutlassJim's numbers and my calculations a 2.5" exhaust will probably be fine. What I'm planning wont be trying to out flow my exhaust. In theory.

You have to take into account the scale. What's needed to make over 500 bhp is not the same as what's needed for smaller applications.

 

[turbowop]

Quoting crankwalk:
Just to go off topic on fpr's I have a 1g auto turbo fpr which bumps up the base pressure and I have a Bosch 044, how does having a stock fpr on a bigger pump compromise driveabilty or economy? The car has a dyno tune/chip/safc and gets 25 mpg and drives like a stock car. Big retarded pumps on a stock fpr with no tuning would cause overrun issues but I would hope people don't do that stuff still anyway.



It's possible to tune around overrun and get decent mileage and driveability, but it's a hell of a lot easier when you use an AFPR that allows for a linear ratio of fuel:vac/boost.

I don't care how other people want to tune their cars, but when somebody comes on and states that the way I do things (AFPR) is a "DSM fad", I get a bit irked. Next thing you know people will be saying that setting base timing via a timing light is unnecessary. /ubbthreads/images/graemlins/wink.gif

 

[Polish]

Quoting Muskrat:
Quoting Polish:
Quoting CutlassJim:
A single 2.5" exhaust pipe is good for around 50 lbs/min of airflow through an engine. 3" exhausts are just a DSM fad where ZOMG I need a 3" exhaust.

/rant



2.5 *will* flow enough to make that power, perhaps.

BUT 3" would make more. Guaranteed.

Someone in the Midwest had a Apex'i or similar type muffler (That necks down to 2.5" inside) on their car and were making around 450whp or so on the dyno. They cut *JUST* the muffler off on the dyno and the car picked up around 50whp. I forget who it was but the car was sold long ago and has been for sale a time or two since then. But to me that is more than enough proof. You can believe what you want.



Actually, based on my calculations your numbers line up with what I said above.

In order to make 450 hp (brake horsepower, not wheel hp. So he was actually making more at the crank) you need to be flowing about 52 lb/min of air through the engine. So if his setup was actually capable of over 500 bhp then yes, his exhaust was a restriction, and opening it up let it breath. a full 3" set-up (or perhaps larger) was appropriate in this case.

However, if your setup can't outflow your exhaust, there's no need to go bigger. Based on CutlassJim's numbers and my calculations a 2.5" exhaust will probably be fine. What I'm planning wont be trying to out flow my exhaust. In theory.

You have to take into account the scale. What's needed to make over 500 bhp is not the same as what's needed for smaller applications.



Fair enough, I still feel there is plenty of power to be gained in lower HP applications as well.

click

^^ Here is an NA K series Honda that picked up power and it doesn't even make 300hp at the crank. And this was just the catback portion. Food for thought.

click

Another Honda, this time a turbo but still started in the mid 300whp range. 2.5" vs 3" exhaust, still 2.5" downpipe. And it picked up a ton of power.


I suppose if you never think you'll make more than 300hp at the crank it's not a huge deal but I still feel the bigger the better.

To each his own. /ubbthreads/images/graemlins/smile.gif

 

[Muskrat]

Quote:
I suppose if you never think you'll make more than 400hp at the crank it's not a huge deal but I still feel the bigger the better.




Fixed. Based on my calculations of course

Those are interesting read's, but I still say that the exhaust was a restriction based on what their set-up was capable of making. Simply changing the exhaust on a set-up already at it's potential wont show a drastic change like that.

I believe that for the plans I laid out a 2.5" system will be more than adequate. Now, I have a "high flow" cat, a glass pack, and a perforated core muffler. Maybe these will end up being restrictions, I'm not sure. It's also possible that I get on a dyno and I'm not making the power I expect. I'll probably target the exhaust as the restriction, first. But I'm not going to change to a 3" exhaust, "because this honda guy saw a 75 hp increase when he did". (After reading through that it comes off a little hostile. Please don't take it personally)

As for the N/A Honda. He saw a 10 hp increase across the board, which to me say's he flowing slightly better at all rpm ranges (makes sense)
But that's not a huge gain. Which to me says that although his 2.5" exhaust was a slight restriction, it was still probably flowing close to his ideal. Or do you think if he opened it up further, he'd see even bigger gains? Why not go to 3.5" or 4".

If you can give me a reason WHY a 3" will ALWAYS produce more power, I'm willing to listen. But just quoting examples isn't going to cut it.

 

[SmoothCustomer]

Those things in the exhaust will definitely restrict flow, but I don't think it will be destroying power by any means. Don't forget you can always punch out a cat*.

*The author of this post does not condone any illegal activities. All suggestions are assumed to be used for off road use only. /ubbthreads/images/graemlins/smirk.gif

 

[Muskrat]

^^ That's what I meant. Wither the cat/glasspack/etc would be restrictive enough to reduce the power I could/should make.

 

[Rausch]

10hp on an N/A motor is quite a bit, as a point of reference. Don't let the smaller #'s fool you, it's not easy making additional power on an N/A motor.

The thing with turbo motors is backpressure, or lack thereof. You already have a huge restriction on your exhaust system, the turbo, so the freer flowing the rest is, the less additional pressures you are introducing into the equation. The easier it breathes, the better it will perform (to a limit of course).

Based on your calculations, a 2.5" system will flow enough, but at what pressures? Just because it's capable of passing xxx CFM, doesn't mean it's ideal. Just throwing that out there. Added restrictions in the exhaust of a turbo car cost you HP. I mean hell, Ideally you'd run the exhaust right out the side of the car, it's be more efficient....

You don't want something so large that the gasses are moving too slow and cooling too far up in the system. The gasses will cool too quickly and slow down again- creating backpressure. (Why 3.5" or 4" wouldn't work in your situation. Besides, you're limited by the outlets provided. A huge step up would only make things worse) You need to get them out as far as you can, with as little backpressure as you can, to get the best performance. It's a balancing act, based on the puzzle pieces you use.

While a 3" exhaust isn't a necessity, I'd be willing to wager that if nothing else, it'll be a bit easier to attain your goals. And besides, with a negligible difference in cost, and the ability to get it just as quiet, why wouldn't you?

Ultimately it's your call, but don't rule out the logic behind the suggestions that are being made.

 

[Muskrat]

Good points. And I didn't realize 10 HP was such a big gain for an N/A. I have no expirience with them performance-wise.

The question still remains though: Is a 2.5" enough? Will you really see gains with a 3" system? I'll have to break out the fluids and thermo books to run some numbers for velocity and pressure.

The power an engine produces is a function of fuel and Airflow, essentially. Without increaseing the airflow, you wont see more power unless you're already not tuned properly (aka fuel delivery).

I'll give you on a turbo application a larger exhaust MAY decrease spool time, thus letting you flow more air earlier meaning you see peak power earlier, but I don't believe you'll see MORE power. Flowing 550 cfm is flowing 550 cfm, wither you have a 2.5" exhaust or a 3".

On an N/A application I can see gains, to a point, from reduced pumping losses. But on a turbo application this is already eliminated by the boost pressure.

I feel like we're saying the same thing, and the only point we really differ on is, "is 3" nessisary." Which, to be honest, neither of us has actually proven either way.

I guess my main point is: if a 2.5" system allows you to flow enough air to produce your peak HP, a 3" system isn't nessisary. The question is: will it? It depends on the set-up, and how much power you're trying to make. This goes back to Polish's statement that a 3" system is always better. Which it isn't.

As far as my set-up goes. I already have the 2.5" system on the car, so that's what I'm going with. If I need to upgrade I will, but not before I see where I'm at with my current system.

I have a feeling I will, however. I'm leaning towards uping the fuel pump, and injector's and trying out the new FP 68HTA turbo. It's come down a bit in price since it's release (only about $200 more than a 16G now) and worth exploring. And I get to keep a stock appearing turbo.

 

[turbowop]

Quote:
I guess my main point is: if a 2.5" system allows you to flow enough air to produce your peak HP, a 3" system isn't nessisary. The question is: will it? It depends on the set-up, and how much power you're trying to make. This goes back to Polish's statement that a 3" system is always better. Which it isn't.



On a NA setup, probably not. On a turbo application the answer is usually yes, IMO. Turbos are all about pressure differential. A bigger exhaust on the end of a turbine equals quicker spool and in the real world, usually translates to moar power.

 

Quoting turbowop:
Quoting crankwalk:
Just to go off topic on fpr's I have a 1g auto turbo fpr which bumps up the base pressure and I have a Bosch 044, how does having a stock fpr on a bigger pump compromise driveabilty or economy? The car has a dyno tune/chip/safc and gets 25 mpg and drives like a stock car. Big retarded pumps on a stock fpr with no tuning would cause overrun issues but I would hope people don't do that stuff still anyway.



It's possible to tune around overrun and get decent mileage and driveability, but it's a hell of a lot easier when you use an AFPR that allows for a linear ratio of fuel:vac/boost.

I don't care how other people want to tune their cars, but when somebody comes on and states that the way I do things (AFPR) is a "DSM fad", I get a bit irked. Next thing you know people will be saying that setting base timing via a timing light is unnecessary. /ubbthreads/images/graemlins/wink.gif



I might be off base but I don't think I'm getting overrun. I think its like a stock 1g bypass valve, some leak at 15 psi and some hold much higher before being modified. I have a liquid filled fuel pressure gauge and just monitoring everything, it always looked fine. Maybe I just have one of those freaks that holds up well that doesnt need to be changed. /ubbthreads/images/graemlins/dunno.gif

 

[Rausch]

Quoting Muskrat:
Good points. And I didn't realize 10 HP was such a big gain for an N/A. I have no expirience with them performance-wise.

The question still remains though: Is a 2.5" enough? Will you really see gains with a 3" system? I'll have to break out the fluids and thermo books to run some numbers for velocity and pressure.

The power an engine produces is a function of fuel and Airflow, essentially. Without increaseing the airflow, you wont see more power unless you're already not tuned properly (aka fuel delivery).

I'll give you on a turbo application a larger exhaust MAY decrease spool time, thus letting you flow more air earlier meaning you see peak power earlier, but I don't believe you'll see MORE power. Flowing 550 cfm is flowing 550 cfm, wither you have a 2.5" exhaust or a 3".





"Is it enough" is entirely too subjective. Will it flow 550cfm+ (Assuming your calculations are correct.), yes, will it do so as efficiently as say a 3”, most likely not. Again the fact that a 2.5” system can flow that volume is not the issue: the question remains at what pressure…(Again, this is important. More pressure=less usable power). The reality of the matter is in this application: Backpressure costs horsepower.

So while you’re theoretically making the same power at the engine with either system, you would be using more of that energy to get those gasses out in a restricted system. Plain and simple. So at the wheels, yes you very well could see more power. Maybe it’s only a few, maybe it’s not.

The point everyone is trying to make, is that barring going overboard (as I noted earlier), bigger is usually better. With that being said, if you already have the 2.5” system, then run with it. When/if you find that the exhaust is a porential restriction, swap it out, and check again, see if you make any gains. Again, more food for thought.

 

[CutlassJim]

Quoting turbowop:
Quoting crankwalk:
^Saying they are mandatory (which they aren't) and then never using them for their purpose is definitely something I see DSM people doing more than other folks.



While not absolutely mandatory, how are people that have them not using them to their potential? The whole point of having one is to keep fuel pressure set to a level that allows for a linear boost/fuel pressure increase. If people want to set their base fuel pressure to stock levels while using a high flow fuel pump, they're using the thing for a reason. Those that choose to tune around a non-linear fuel curve are free to do so, but using proper tools/tuning techniques to acquire the best possible power/driveability/economy is certainly not a fad. There is no argument that max power can't be made with the stock FPR, but it forces you to compromise on economy and driveability.




And I'm assuming you have logs of fuel pressure vs rpm and or load to back up this "overrun" that people like to throw around. Cause it would be the first one I will have seen. And maybe myself and others who's cars I modify are just lucky because with a stock 1G FPR (and it's crappy lower base pressure) and a Whinebro 255 pump I get no fuel pressure creep at idle or at any rpm free revving the engine. I was going to use a 2G FPR and remove the restriction pill on the return but even then the return line hose ID is smaller, eff dat. I just use 880's on my 16G to compensate for the lower pressure. Even though, up to a point, I've read that higher pressures result in a nicer and more atomized spray pattern.

Also take this as a grain of salt because it's coming from a guy that crushed his stock FPR (a Buick TR trick) and overdid it to the point the injectors leaked and when I took the plugs out and cranked the motor over fuel shot out of the cylinders and bounced off the hood and gave me a bath. /ubbthreads/images/graemlins/rofl.gif

 

[CutlassJim]

DOUBLE POSTING FTL! But I didnt' think this fit into my previous post.

COLD startup. Wally 255 stock filter, stock lines, stock rail, stock 1G FPR, 880's



The ghey engine bay.

And I shouldn't even be talking about small exhausts, here's the current set-up.

 

[prove_it]

I'm running 2.5 inch CRUSH bent exhaust with a 2.5 inch high flow cat and a chambered muffler. Yes I know I will get flamed for this, but with a stock turbo at stock boost levels with an engine running 8.5:1 comp, and a stock intake cam with a HKS 264 exhaust cam, with high flow valves and a port and polished head breathing through stock IC piping and intercooler, a stock MAF with a K&N. I am currently running it around the 11.5-11.8 fuel ratio with about 15 degrees timing. I'm seeing about 230whp with that exhaust. It's restrictive, crappy, and has a cat and a chambered muffler. I'm still seeing about 60whp over stock at 9lbs boost and a 14b. It does die after 6k due to the stock intake piping and stock MAF and this exhaust.

Could I make more power with a 3 inch straight through exhaust, yes, for sure. But if a 3inch was so damn important then why am I making 60whp over stock with such light mods? Yes when I go with a 16G I will change the exhaust for better and the IC too. But really it's not the most important thing you need to make big power. I've seen evo's with stock exhaust pushing 320whp before. It's not a mandatory upgrade but I will agree that it does make a big difference in power, it's just critical.


Oh and I'm seeing about 9lbs at 3,000 rpms too.

 

[Rausch]

The whole point was the OP posted a prospective mod list, and we suggested a 3" exhaust, and possibly more headroom in the injectors. He already has a 2.5" system, so it is what it is.

For the record, 264's and increased compression go a LONG way in making power.......

I would also like to add: /ubbthreads/images/graemlins/eek3run.gif

 

[CutlassJim]

^ 2nd that.

 

[prove_it]

Sounded like the OP was concerned the exhaust wasnt' good enough. I was only letting him know that even a crush bent exhaust will still flow enough to be good, and like I said a bigger system would be better. I just don't want to see him JSB for a few months waiting for an exhaust.

 

[turbowop]

Quoting CutlassJim:



And I'm assuming you have logs of fuel pressure vs rpm and or load to back up this "overrun" that people like to throw around. Cause it would be the first one I will have seen.



/ubbthreads/images/graemlins/confused.gif Who needs logs? You can see the higher flow fuel pumps overrun the stock FPR with a simple fuel pressure gauge mounted at the filter if need be. If it's higher than stock base fuel pressure, it's overrun. It's also overrunning the stock FPR at anything in vacuum since it can't even bleed off enough pressure at zero boost/vac.

I'm not sure what you're trying to prove with your video? I never said the car wouldn't start and idle without an AFPR. /ubbthreads/images/graemlins/uhh.gif

Like I said already, it's a tool that makes tuning easier. If you wanna run without one, have at it, but don't knock the guys that use one. /ubbthreads/images/graemlins/crazy.gif