What is the hp gain with headers and exhaust modifications?

 

A very reasonable question. I never thought that exhaust or headers would result in much power or performance improvement but I could be wrong.

 

Headers and larger intake manifolds were used to increase horsepower in muscle cars back in the 60s and 70s. The oem cast iron manifolds restrictions were unleashed with the modifications resulting in increased power. I'd like to think a completely improved exhaust system would produce a noticeable difference in performance/horsepower. If not, then why pay what it costs to make the modification?

 

Is it possible that on a modern car such as the LC 500 (Compared with 1960-70s cars) the engineering has advanced and there is not the same degree of restriction or limitations with regard to the exhaust and manifold systems? I imagine that a dyno test could compare the horsepower level of a stock exhaust system versus an aftermarket system. It’d be a way to determine money spent and horsepower gain ratio.

 

I experienced significantly increased power in my Lotus when I changed out the exhaust. However...........

- the new exhaust was a larger bore pipe which is where most of the power increase came from
- a freer flowing cat and muffler was installed
- a change in the pipe routing to make it straighter was performed
- the exhaust manifold was smoothed out and ceramic coated

I would suggest that a simple exhaust system exchange with the same bore, pipe routing, etc. isn't going to do much for power other than a placebo effect. Especially on a car like ours that has been tuned as well as it has. Even a freer flowing muffler and/or cat doesn't usually give you more than a handful of ponies.

 

I believe exhaust is about 10-15 whp and headers are about 20 whp. OEM cats are very restrictive.

Personal experience with FBO from an ISF engine.

-Josh

 

Thanks Josh. Was there a performance difference that you could detect while driving?

 

35 ponies in total isn't a lot for the cost of a new exhaust and headers. Just sayin. If it was time to replace it all then perhaps. It's about a 7% incease so it might not be a noticeable difference jn 0-60. If someone has some before and after numbers on that it would be great to see them.

 

for resale value mods are a no no.

 

Agreed it does not seem to be a particularly good value proposition for performance enhancement but to each their own choices. It seems that the bigger attraction is probably a desire to change the exhaust volume level and/ or character.

 

might one observe that any modification to increase noise or power will bear the consequence of
increased heat, and stress , and decreased engine life ?

 

Not just on an LC, but an exhaust rarely adds much power to a naturally aspirated engine. Lexus isn’t some speed shop that puts any old angle in the exhaust to make it fit. I guarantee that there was computer simulated exhaust gas flow analysis before they even started to prototype the car in metal. Exhausts and Cats are done to change the sound in a normally aspirated car. Or, just to say you did. (No offense to anyone.) You’re not doing it to free up a bunch of power for a low cost. If you want to get gains on the cheap, or large gains period, you’re going to want to be working with a forced injection car (turbo or supercharger). You can gain 100hp for a thousand dollars with just an ECU flash on a Porsche 911 Turbo. You could change the flash, intake, and whole exhaust system on an LC500, something that’d cost juuuuuuuuuuust a bit over a grand, and I doubt you’ll get close to 50hp. As someone mentioned, unless you find a retail buyer who wants exactly what you put on your car, modifications normally have zero resale value while still on the car and sometimes hurt the value.

 

i have never bought a modded car, theyre usually for sale because of "issues" where they dont run quite right..

 

Salient points!
I believe that Lexus has put significant effort and time into getting the exhaust system tuned to their desired outcome. I’d be perfectly content to leave their finished product as is. Having said that I absolutely understand the motivation to modify and customize to establish one’s own personal preferences. Essentially you own it and are free to do with it as you please.

People do complain about no powered trunk opener,lacking the lastest tech, no fold down rear seats etc. However in terms of built quality, fit and finish, suspension and normal aspiration V8 drivetrain Lexus got it right. In my opinion these areas are more important,

 

Bingo. I don’t mind modding a car on my own. I can do a ton of research and decide if I’m comfortable doing it to my car, and knowing what could go wrong so it’s easier to fix or know what might blow up. Do I trust that some guy didn’t buy a bunch of generic parts off of eBay, or even bought legitimate parts from a proven tuner that still has a tiny fraction of the R&D budget of a car manufacturer, and added the parts in some weird combo and hope it worked? I … do not. I had a custom tune on the previously mentioned Porsche, and while I was talking to the shop owner while the car was on the dyno he pointed to a car and said “it’s been here for months, after this guy brought it in with a ton of mods that he claims used to work, and we have to take the whole thing apart to figure out what’s wrong with it. We’re checking for leaks and malfunctions in every single part, and every fix causes some other issue.” I’d buy a car with an aftermarket catback exhaust. Maybe an intake, but probably not. Flashes, modified turbos, and headers? Nope. A modded suspension? I’d need to road test it A LOT and have my mechanic look it over.