carose725

I've heard over and over that the crossover pipe on the 3.0 is a huge killer to the engine, and seeing diagrams of the pipe and exhaust flow through it, i can tell it is a terrible set up. But what i was wondering is if anybody has removed the crossover pipe and adapted new piping down to the cat . seams to me that would give tons better flow. If anyone has done this could you give me some info on it. Thanks

Churnd

If you could get around the space issue, you would have to block off the port that the crossover dumps into on the drivers side manifold somehow. Welding a plate over it would work fine. Other than that, you'd have to remove the crossover completely and either modify it so it'll point down along with the current downpipe or fashion your own pipe to run to the passenger side manifold that'll fit through as the crossover did. That's a lot of work... just get headers.

Actually, from what I've heard... the engineers that designed the crossover this way weren't as stupid as we all think. There's actually no restriction from having the crossover pointed the way it is. Something about how the cylinders fire and the pipes being tuned specifically for that. If you've ever seen the crossover, it's got a big bulge in the middle of it, and I'm pretty sure that bulge is for tuning purposes.

What you need to do is just get new exhaust piping from the downpipe back. 2 1/4" should work great. Match that up with a high flow cat and muffler, and you're set. Or at least that's what Tim at DOA says.

carose725

so you estimate it wouldnt be worth trying i guess.

Yoter

By removing the CO pipe you will gain flow & HP IMO. By removing it you can also then have a true dual exh. instead of single into duals. MikeT223 was going to do this mod but got busy on other projects. He was going to from the sounds of it yank the CO pipe, port the exh ports, and turn the 3.slow into the whoaaaaaaaaaaaaaaaaa lol. I am going to see if I can pick up the 3.0 exh manifolds tomorrow when I pick up some other parts. If I get them that may assist him with his experimenting. I just dont see how some can say it will not help. flow traveling into direct flow is for sure going to hold it up. No off. Churnd.

Also I have a buddy that has this mod done to his 4runner but it came that way when he bought it. So atleast we could have a model to copy from if Mike is willing to be the doctor on this operation. lol

carose725

can you get some pics of his modded crossover pipe for us. i think it could be very benificial to many 3.0 owners if this mod were visible.

Yoter

Sure can try. Thats a tight area to try and photo but I will try. Plus he just did a body lift so it may not be as tight as im thinking. Blue

carose725

Thats cool i cant wait to see them.

4Runner 4Play

Hey Carose, sorry to hijack the thread but I got a question bout your exhaust set-up. I too have a 93 runner and looking to upgrade the system. As you already know the stock pipes are all 2" and Iam thinking of doing what you did. ie. from headers to tailpipe convert to 21/4" Including cat and muffler. Thinking of going with a Walker High-flow cat and the Dynomax super turbo muffler. I guess the question is do you have any advise on this and how do you like the set-up? BTW. really good idea with the cross over pipe. I thought bout that one too. But I gotta take the mods slow. You know, dont wanna lighten the wallet too much too fast. Later, Lee

carose725

i just got my exhaust done two days ago, i got a dynomax super turbo muffler, and a dynomax high flow cat from summit racing. i diddnt think the price was to bad about $98 for both. i had them installed the day i recieved them. 2 1/4" piping. they sound pretty good to me throaty but not annoyingly loud. i also noticed better acceleration on the highway. diddnt really feel any gain in torque though. the muffler shop i went to had it all welded up in about 40 minutes and only charged me $65 to weld it up and they even bent the piping and made me a custom tip come out in the stock location.

Churnd

None taken. I'm all for finding more power, and I applaud those who have the guts to try something new.

I hate to be the voice of doubt, but I still don't think it's gonna work, unless you've got plenty of money and time to fool with it.

Now about that running pipes off of each manifold as duals... why? I don't see that being any more powerful as using a well tuned crossover, considering you match up the backpressure numbers for each pipe. Low end would be non-existant, it seems. I dunno... maybe it would work. But I'd have to see before and after numbers to believe it.

Yoter

Well the project has run into another obstacle. I was unable to get the exh manifolds today from the seller that I had to travel to buy from (4 hours round trip). So I cant mess with the idea or get Mike the parts yet. I am going to keep my eyes peeled for the parts. Blue

blackrunner91

hey guys, i've got another exhaust question. I've got a 3.0 and I was thinking about maybe running 2.25" pipe from the down-pipe back a few feet into a flowmaster or magnaflow, then have maybe a turndown or something. I do not want to run a cat b/c by law you don't have to run one in Alabama(that's where my truck is tagged). I did this on my '86 22re 4runner and could tell a nice difference in power without the cat. I also want the turn-down b/c I like the look with no exhaust pipe. It worked very well on my '86. The main question that I have is, if I put the o2 sensor in the same location on the new pipe, will the truck still run correctly? i think that if it runs right, that would be one of the best increases in power that you could get from a 3.0 exhaust.

Churnd

Mine didn't... but you might have different results. For what it's worth, I live in MS so we have the same environment.

I say try it... it doesn't cost anything. If it doesn't work out, weld in a high flow cat and that'll be the answer to your problems.

With mine, I didn't have enough back pressure and for some reason my idle fluctuated erraticaly a lot.

blackrunner91

Churnd, hey man, so you're saying that your truck ran good with no cat? what did you do to fix the eratic idle?

Churnd

No, I meant it ran bad with no cat. No backpressure and the idle fluctuated. You could hear the exhaust pinging around in the pipes if you listened close enough. That noise was a telltale sign that I needed more backpressure. It was fine for high end, but I don't race.

Yoter

Everyone seems to think that if you remove the cat your rig will not only stink to high hell, be loud as hell, and run like hell. not true. yes the stink is not avoidable and the loudness is well LOUD. I had my cat off for a week and a half and the noise, smell, and thought of what I am adding to the enviroment made me buy the magnaflow car sound high flow cat. I assume my previous cat was gutted because I do not have as much flow as then. Yes you would have almost to much flow without a cat but its not worth it. Go high flow.

blackrunner91

okay, here's what i'm thinking now:
from downpipe use 2.25" pipe back to a high-flow cat, then either a flowmaster or magna-flow or other, then a turndown immediately after muffler. sound okay?

Churnd

Perfect.

ALEKATNM

My 3.0 has the cat off and kept stock muffler. Engine lite is on and it started with a quite ping/tick. now it sounds like the motor is toast. in fact I tried to trade it in last week and two dealers told me it was toast. The ping/ tick is way loud now and I definately think its gone. Could I have toasted the valves or something? BTW im getting a TPS code of the comp. I was getting control module code, but I ditched my Boschit plugs to denso, and that was the point when the ping/tick really got bad. My insurance is going to help with them motor if thats what it is, so putting in a long block will be nice. If I do put in a LB Im going to go with NWOR headers and crossover right off the bat. to a high flow dynomax. Would rather have the darn thing on the road though.

Firefyter-Emt

Bull Poop!! The design is flawed. The RT bank entirely dumps head on with the exhaust gas leaving the LT bank. Then they must be forced down at a 75ish degree angle to the head pipe. There is not was the order they clyinders fire will have any bearing on this. at 1000rpm, it is pretty much a solid stream of exhaust gases. That manifoild design is a leading factor in the failure of the # 5 exhaust valve. Now if you or any one ever can show me flow charts to prove me wrong, I will eat my crossover! BTW, the pipe is the same diameter, the "bulge" is the heat shields. I also looked at doing this and I think in a way, this would be the answer (short of headders.) But I would drop the stock dump on the LT manifold, block it off with the old headpipe capped off and run both out where the crossover holes are. This would make them flow more eavenly I would think. Problem is, that in the long run.. it is a crap load of work where there are very good headders that are custom fit and flow better than the manifolds ever will. Plus they will dissapate the heat better.