al-ex-us

I'm trying to purchase an SAFC for a TANABE cat-back exhaust system on a 98GS4. Anyone have ideas on where to purchase it and how to set it up?

JBrady

You can tune the engine for more performance but no tuning mods are needed for installing an exhaust. The exhaust will not help power on an otherwise stock engine. Headers are a different story as are intake mods and of course the mentioned tuning.

al-ex-us

What (brand or configuration) would be best recommended for significant horsepower gain (over 15hp)?

beez43

iTrader: (6)

get intake also..

JBrady

Rock-a-lex has made the most power that I am aware of for bolt ons with a tune. Here is a very lengthy thread which gives a fair amount of info.
https://www.clublexus.com/forums/per...pointment.html

Personally, I would recommend the headers with a tune. For further real performance gains get the PI torque converter followed by a limited slip differential.

If you wish you can start with the torque converter.

Exhaust mods other than headers are primarily for look and sound at these power levels.

MDSC

iTrader: (3)

I tend to disagree with this statement, but i guess we'll find out. Im going to dyno this 2000 400 bone stock, then cat back 2 1/4 custom made exhaust with a drop in k&N i would very surpized if i didnt gain at least 10rwhp+ on this car from doing that. headers are nice but it all comes in stages. I also see that people are doing 2800 stall converters and these cars from looking at the dyno graphs arent hitting peak trq unitll 3600rpm. I would say that getting a 3200-3400 stall converter would be alot more suitable, you dont want to hit peak trq right away but you want to be a few hundred rpm away from it when you launch. Youre not using all of your trq if you only hitting 2800rpm right off the line, especialy from my experience when the converter is rated at certain stall speed it takes a while to even get it broken in to be close to that number for example on my camaro my 2800 stalled only to 2200 when it was new and 2400 after a few months of break in.

JBrady

MDSC, you have some quick/fast rides. Your experience will be good for this board.

I am not sure if you are familiar with me yet but I have been a proponent of exhaust mods for a long time. I was recommending 2.25" for these cars back when the headers first came out. A number of people have made 2.25" and also 2.5" systems. I have yet to see any solid before and after dynos for these mods alone.

Hopefully you will do a before and after. On your before do a run with and without the K&N. That would be interesting. On my particular car I do not recommend the K&N due to the stocker being very good and having much more filter surface than the K&N offering. This may not be the case for the GS but is in fact for the LS400.

Once your exhaust is built do a before and after with the K&N also. This should give us the results of just the exhaust, just the K&N as well as both together. Good to have data.

I have said before more than once that I am certain a better than stock exhaust can be built... BUT... it is also likely that many/most attempts will either hurt low end power/torque without gaining top end. The design and build quality is everything. The stock Y pipe setup does a great job at low RPM scavenging and being mandrel flows better than expected. Have seen it support nearly 400rwhp with supercharged cars.

Again, yes, it can be improved upon and I look forward to your testing. Just make sure it doesnt do something negative like making the engine less responsive. This happened on the first header car. I donated a very nice 2.25 to 2.50" two-into-one merge collector and dual 2.25" were built from the cat outlets. Dyno testing showed ONE horsepower. Driving showed a big loss in response in lower RPM street driving. Obviously a poor trade.

By all means build and test and report.

Until then, my statement is a very good (and affordable) recommendation... run the stock exhaust WITH headers.

MDSC

iTrader: (3)

after all i think i might have to go with Intake set up over drop in we'll see, its my g/f car i was giving a green light to do exhaust and some other stuff she just got the car a few weeks ago. I own an exhaust shop and will be making my own stuff. I'll post pics later she leaves on vactation on the 19th i have the car in my posession then Thanks for the heads up the exhaust its def possible ive seen where cars gain absolutly nothing from doing exhaust, i was hoping that wasnt the case with this car. I stand by what i said earlier though 3400 stall its a 13 sec car right off the bat with good weather and right track altitude especially judging by mph. IF you make 260rwhp+ and hooking on a street tire especialy with gear your set up is capable of much more, with that much power and street tire the car should be blowing tires off on the launch no matter how sticky the serface is even at the track.My 94z28 when bone stock ran 13.9@99 w 2.0 60ft, with cold air,catback,cat delete, 2800stall, pair of nitto 17" drag radials car ran 12.96@104mph in full street trim with stock manifolds.

JBrady

Yup, these cars should go 13s on stock power. Check my sig, that 14.2 was on a 2.2 60ft (best doable on stock rubber, open differential and terrible drive by wire throttle controller). If I had limited slip alone I could probably pulled a 2.0 and a high 13 and my car is the heavier LS400.

Post pics and details of your exhaust mods. Get some replacement catalyst outlet 2 bolt flanges so you do not have to cut up the stock system... you may decide to put it back on

Here is a pic of the merge collector I donated to the effort I described above (it is on the right, the left one is 2.25-3.00, right one is 2.25-2.50)

3UZFTE

Jbrady, What would you do if the stock Y-pipe happened to be leaking or rusted, would you have another one made to replicate it or would you just possibly run a x or h pipe to cross over. The reason why I ask if that is because I had an exhaust incident not to long ago, and it seems like the Y-pipe is in terrible condition, in more than a few spots. My friend and I are going to make a custom exhaust ourselves, so I am curious as to what your thinking. My overall goal is not power, So i am only thinking of 2.25-2.5 as those are my power levels. I am trying to go along the lines of cheap, but nicely done with a little bit of rumble when I touch the load pedal. Some input would be appreciated, as always...

JBrady

Glad to help if I can.

It is hard to create a pipe that works better than the stock pipe and easy to create a pipe that does not work as well. Hate to go to the trouble and expense only to loose low end, crisp-ness of response and feel and have to pay for it

Stock pipes are probably available from wrecking yards or from people that have built replacement pipes. I bet most cut the flanges off the stock pipe to make a new pipe so that may make most take offs un-usable without re-construction.

I came away from the above described effort with an appreciation for the relationship of the feed pipes to the fed pipe in Y pipe design. I think 2.25 pipes are too large for a single 2.5" pipe to transition as efficiently as the stock pipe with 1.97" pipes feeding a single 2.36" pipe. Total cross section area reduction on the stock = 26.3% (total csa of the two feed pipes vs. total csa of the fed pipe) with the 2.25s feeding a 2.5 that ratio jumps to 37.5%. It would take a 2.75" fed pipe to better the factory.

In addition the factory Y section is what I have named a nozzle collector. A nozzle collector places the point of acceleration at the end of the feed pipes instead of the end of the collector. The result is a one way collector that fights reversion while supporting the same peak flow. Very functional. Better than the picture I posted above for a street engine.

The key to remember is the ONLY time larger pipe capacity is needed is near peak power. Below that point a smaller pipe than stock would be fine. The smallest pipe that supports peak power is ideal on a street engine.

This is why I recommend stock. Not that it cannot be improved upon but rather it is more likely that a worse system will be built. Get a stock pipe if you can.

MDSC

iTrader: (3)

What i think i'll do is Take out the first resonator and replace it with 2.25 x pipe and then build my own rear sections with 2.25 mufflers and tips(magnaflow most likely) and leave the stock exhaust from x pipe to the rear flanges since its already mendral bent and has 2 resonators built in.

JBrady

What type of X pipe? There are several. The universal Magnaflow one is internally a 2.5" pipe with 2.25" ends welded on the stamped body. The window type (like Dr.Gas) work more like a combination X and H. The scavenge type (like Burns Stainless) is a merge collector X pipe and is tuned for the application. Again, the stock Y uses a Nozzle collector which works better than most imagine. Whatever you try... if you can keep the stock pipes intact for re-installation you can do easy back to back testing which will help this board and give you the parts you like the best. This is a great oppty since you have a muffler shop.

Update: it appears Magnaflow may have changed their X pipe design. The new design looks much better but I am guessing that it still uses the same core size (probably 2.5" with whatever inlet-oultet size is ordered for fitment.

Update/Update: even though Magnaflow shows the "new" style X pipe on their main X pipe page... when you select item # 10790 it shows a picture of the OLD style

Old style:


New style:


Dr. Gas style:


Burns Stainless style:

3UZFTE

Thank you for your knowledge, it's much appreciated. In the mean time, I will look for a stock Y-pipe, as mine is pretty nasty after this person welded it, and needs more work than I want to invent. Thanks again.

MDSC

iTrader: (3)

well i apriciate all the advice i would think the factory x pipe/resonator would be restrictive, it looks like it but after reading what you say i might just cut out the rear resonators and do rear sections. I do own a muffler shop but i dont own a dyno , so i cant just keep changing exhaust out and head to the dyno and pay $$$ every time. IT would be nice but i just have the time to do it work late hours all the time. Is there a picture of Burns style x pipe like cut open(exposed)? i was going to use an old style magnaflow, cuz i can buy one real cheap. But if can get an idea of how the Burns style is made i can duplicate it, if not i'm leaving the first resonator alone.
Edit: i can easily make something like this myself http://www.jegs.com/p/JEGS/JEGS-Narr...30498/10002/-1