Exaust Clarification

[NSUCK]

Hey, I have a 95 sc400 and I've read all of the exaust threads on this site and a few others. I still havn't seen exactly what I'm looking for. I want an exaust that will sound mean, and give me good gains.. mostly looking for the power but want a good blend of both. I live in cali (sac) so I'm not exactly sure what I would need to pass smog

this far I'm thinking
2.25 w/ x pipe
and magnaflow mufflers
I've seen I need 3 cats for ca? and do I need resonators as well or can thoes be left off?

thanks for any replies

 

[Peewee]

All the gains are in the headers, there is not much to gain by changing anything behind them, maybe 10hp max.

 

[NSUCK]

alright, im not sure if there are any headers I can even get that will pass CA emmissions? but as far as the exaust goes, does that sound about right for what I was looking for?

 

[6spdSC4]

What kind of gains can you get with the headers? I'm so on the fence about what to do with my car! I want to sell it and buy a TT Supra, then the next day I want to keep it and SC it bla bla bla...for now I think I just want to get it a little quicker than what it is now. I've got the BFI already and want to do the full exhaust. I've heard some bad fitment problems with the US spec models, but I don't remember exactly what they were. I believe the headers are around $700-800 US? How much would it cost to have them installed by a shop(assuming the install isn't easy enough to do by myself w/o a lift)

 

[Peewee]

On a stock ecu, maybe 10-15hp max.
Nothing monumental.

 

[6spdSC4]

But basically a full exhaust would be good for 20-25hp at the crank then? Is there any type of piggy-back for the US spec stock ECU that doesn't require any real dyno tuning?

 

[Peewee]

I'd probably say closer to 15-20hp at the crank.

I haven't seen the SC400 headers, but I assume they aren't as retrictive as the Crown ones, and therefore the gain will be less.

As for the piggyback, depends how much you care about your motor.

 

[6spdSC4]

Well she's got 105k on 'er now and she's my daily driver so she's gotta last me a while!

 

[Peewee]

If you get say an SAFC-2, give it a good hour or 2 on the dyno.
Add a bit of timing, make sure the fuel is right, and bam, that will be enough.

 

[6spdSC4]

Would the SAFC help gain some power as well or would it not really be noticable?

 

[JBrady]

I'd probably say closer to 15-20hp at the crank.

I haven't seen the SC400 headers, but I assume they aren't as retrictive as the Crown ones, and therefore the gain will be less.

As for the piggyback, depends how much you care about your motor.

Peewee, I must say your comments surprise me. Your engine is running around 60+rwhp over stock... that is around 75-80hp gain at the crank. I personally do not believe your dual throttle body set up is helping much if any. I would think the majority of your gains ARE from your headers...

 

[6spdSC4]

JBrady, do you think Peewee's guess on the power gains w/ the headers and full exhaust are accurate?

 

[Peewee]

JBrady, I'd say of that 75hp gain, about 10-15 is from the intake manifold, 20-25 is from the exhaust, but the majorirty (30-35hp) is from the aftermarket ecu.
I am running a lot more timing in the top end compared to the stock ecu.

Have a look at what some of the Soarer guys have.
They have the Tex/Rush headers, full exhaust, CAI's, etc, and they are only 20kW over stock.

 

[JBrady]

JBrady, I'd say of that 75hp gain, about 10-15 is from the intake manifold, 20-25 is from the exhaust, but the majorirty (30-35hp) is from the aftermarket ecu.
I am running a lot more timing in the top end compared to the stock ecu.

Have a look at what some of the Soarer guys have.
They have the Tex/Rush headers, full exhaust, CAI's, etc, and they are only 20kW over stock.

Peewee, I think you are seriously underestimating the value of a good exhaust. The GS400 was rated 300hp/310tq while my car with an identical engine but more restrictive exhaust is rated 290hp/300tq. This 10hp/10tq difference is primarily from the 60mm vs 50mm center resonator size.

On your car you estimate 15hp intake, 25hp exhaust and 35hp in tuning. This is VERY tough to know without measuring each step. I would suggest that the intake may not make any extra power but giving it 10hp leaves 65-70hp. Even if the tuning gives 35hp (arguable) that leaves 30-35hp for exhaust. Now, without the exhaust the tuning would not yield as much power. With the stock exhaust you may only see 20hp from tuning. If you measured at that point, then added exhaust and tuned again you could say the exhaust was worth 50hp.

Bottom line is that an engine is a system that each component effects. Some "upgrades" can actually cost power (like open to engine heat air filter elements". So, when someone upgrades several components at once it is hard to know what each was worth. One combination could make more than expected and another less.

Knowing how terrible the stock exhaust are I would suggest a minimun of 20hp and with proper support upwards of 50hp.

 

[JBrady]

Peewee, how much power do you think you would loose if you put the stock exhaust back on?

 

[Peewee]

Now, without the exhaust the tuning would not yield as much power. With the stock exhaust you may only see 20hp from tuning. If you measured at that point, then added exhaust and tuned again you could say the exhaust was worth 50hp.

True, but exhaust without tuning would yeild about the same results as tuning without exhaust.
Its been done on many guys running the rush imports/tex headers and a stock ecu.
They go from about 125ishrwkw to 145ishrwkw.
Then they get the unichip done, and another 20rwkw is made.

As you said, without everything, improvements are small.
Tuning on its own is probably 20hp
Exhaust on its own is probably 20hp
Tuning and Exhaust is probably 60hp.


If I was to go back to the stock log headers (remember I had crown headers, not soarer headers), then I'd say I would loose probably 20hp, especially in the top end. But I would also need to have a good hour on the dyno to retune it to the restrictive exhaust, and I would probably loose another 15hp.

In the comparison of these two dynos (http://www.conceptual.net.au/~peewee/dynocomp2.jpg),
From the 211hp run to the 241hp run, all that was changed was from the Y-pipe back (went from twin 2" into single 2.5", to twin 2.5" into single 3") and the intake manifold was put on. (ie, the extractors were on for the 211hp run.)

 

[JBrady]

From the 211hp run to the 241hp run, all that was changed was from the Y-pipe back (went from twin 2" into single 2.5", to twin 2.5" into single 3") and the intake manifold was put on. (ie, the extractors were on for the 211hp run.)

Peewee, so on the 211hp run you had your custom 1.5" headers into 2" pipes into a 2.5" single. Had that combination been tuned or was that running on the standard ECU? I understand that you may also have had the extra throttle body but I don't think that helped you. Consider that the 300hp vvti 1uz uses a single 75mm throttle body on a MUCH better intake. The early intake is a good torque design but a limited power design. Adding more throttle body is not going to change that.

So, stock engines typically dyno at 175-180rwhp. Yours with headers made 211rwhp. Unless you tuned that combination it would appear that you gained 30+hp from headers alone. You then increased the size of the secondary exhaust and tuned for a gain of another 30hp. Did you dyno with just the larger secondary system? I would be interesting to see how much power your engine made on the dual 2" x single 2.5". Consider my engine has a single 1.97" center resonator and a single 2.36" center tube. (that is all going to change, warranty is about up and my headers are getting close)

 

[Peewee]

I've never run a factory ecu, so that 211 was tuned.

Most people get about 200rwhp on stock headers with a tune.
So I got about 10hp with extractors, tune, and restrictive exhaust (read: 2.25" cat and 2.5" single system). 5000rpm up it definately lacked punch.
Another 30hp was freed up with the rest of the exhaust being completed, and the addition of the 2nd throttle body.
About 20-25 would have been the exhaust, with only 5-10hp from the intake manifold on stock cams.

After I get cams my intake manifold will be more useful.
But at the moment it just helps throttle response, while not doing much for peak power.

 

[elhsupra]

Just to add some more dyno info. Don't know if it will help.
I have an 82 Supra with a 92 LS400 1UZ. It is all stock including ECU except Custom 4-1 headers and exhaust. Exhaust is similar to Peewee with a dual 2-1/2" into dual 2-1/2" cats Y into single 3" into Magnaflow with dual 2-1/2" outlets.
http://www.geocities.com/elhsupra/Dyno.html

 

[Aikidostudent]

New exhaust

Hello, everyone have a question,

I have a 1993 Sc 400 made 2 changes with the car.

1. High flow filter
2. Too car to exhaust shop and the cut off almost all the exhaust. All one can see from under the car is, the factory headers,cats, and about 1 to 2 feet of the factory stainless exhaust, rest of it is gone.Had put on 2 1/4 in stainless steel exhaust but on , running true dualls all the way back with H pipe in the front middle going into a pair of stainless steel Flowmasters series 40'tees . loud and sounds great , plus the resontars are gone two.

Question what type of horsepower gain should i get from this and where I gain and loose the torque area?? Plus does the factory ecu ajust itself within a week of driving or do i need to reset the computer but taking off a terminal at the battery for 5 to 30 minutes. to reset itself for the new flow enchancement. Not sure what to expect need some info help thank!!!!!!!!!!

By the way Lex I am not a cheap Lexus owner when it comes to money spending, Just spending wisely at first and going from, Need to know what other type of performance goods I can at to!!

I do have the 4 to 5 grand range for a FI just need to know what kit is better the single turbo deal u offer or the supercharger and if u are still offering free install. Waiting on some reply thanks Dudes!!!!!!!!!