HP increase from 290hp stock 1uz vvti

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scfou

New Member
Messages
53
Location
West Side
Fellas, how much of a HP increase will I achieve with this planned setup. Also, tell me if I'm doing anything wrong here. I have a V8 98 vvti SC400 Lexus. I've already customized my stock exhaust system with 2.25" "H" piping all over, removed all resonators, and retained stock mufflers. It sounds pretty mean so far. The next mod I did was the custom BFI mod. I should be right around 300hp right now. Now I'm also thinking of removing the stock cats as well, which some say will increase about 20rwhp; is this true? The car should also run richer which I should probably get it tuned with a safc controller. Now how much louder will this be without the cats? Remember I still have the stock mufflers. I'm also throwing in a 75 shot zex nitrous wet kit following. Now will there be issues of adding a wet nitrous kit after I tune the car with the safc unit from having no cats, as I'm sure the tuning will be mostly leaning out the rich fuel mixture. How much extra HP will I be able to achieve with all this?
 

scfou

New Member
Messages
53
Location
West Side
I'm done with the intake and exhaust. I personally don't think expensive aftermarket parts such as intake and exhaust would do much better over what I've done already. Isn't intake exhaust on the 1uz motor just around a 10hp increase? I would like more info on the removal of all cats, safc tuning to lean out the extra fuel from the removal of both cats, and whether a 75 wet shot of zex would conflict with the leaned out air/fuel.
 

JBrady

Moderator
Messages
1,776
Location
Houston Texas
Keep the cats, they are very high flow metal substrate and enhance low end performance without hurting top end. NO way will removing the cats give you 20hp.

You should get headers, tuning and a torque converter to make the car quicker/faster. S&S headers can be used but they move the cats down about an inch so some customization would be needed. If you are dead set on cat removal pick up a set of the IMF headers. The stock SC manifolds are very restrictive. Tuning from the stock 11:1 ratio to 12.5 will help a great deal. The torque converter will give you much more torque at the wheels off the line for a much quicker car if you learn to launch without going into severe wheel spin.

IF I did the IMF headers I would re-install the cats in the center tunnel area staggered to make them fit nicely.
 

scfou

New Member
Messages
53
Location
West Side
Right on JB. Yeah I did more research about the cats just now, and have decided to keep them on. The last thing I want is for my lady to complain about gas smell inside the cabin. Also, I found out that it's just about a 5hp gain. It's funny how this other guy said to me that his 2000 is300 made 200rwhp after removing the cat, and that's all he really did. But in any case, it looks like my next move will be headers but they're so expensive! Then after that I will get a 3600 stall converter. And when everything is tuned properly via a s-afc1, I will also throw in 75 shots of wet ZEX. Hopefully that'll get me in the mid 13's, what I'll be happy with on the life of this ride.

Sounds about right JB?
 

JBrady

Moderator
Messages
1,776
Location
Houston Texas
Right on JB. Yeah I did more research about the cats just now, and have decided to keep them on. The last thing I want is for my lady to complain about gas smell inside the cabin. Also, I found out that it's just about a 5hp gain. It's funny how this other guy said to me that his 2000 is300 made 200rwhp after removing the cat, and that's all he really did. But in any case, it looks like my next move will be headers but they're so expensive! Then after that I will get a 3600 stall converter. And when everything is tuned properly via a s-afc1, I will also throw in 75 shots of wet ZEX. Hopefully that'll get me in the mid 13's, what I'll be happy with on the life of this ride.

Sounds about right JB?
3600rpm is too high if you want to enjoy driving it on the street. 2800rpm is as much as you want. I am contemplating a 2600rpm one myself.

I am modifying the S&S headers for my 99 LS400 as they are too short and the flanges are 180 degrees out of position. Similar problem with your SC except they are too long and the flanges need to be repositioned. I ordered my headers with the flanges only tack welded on so that I can cut them off easily. I would do the same if I was working with your car and shorten the collector slightly and weld the flanges on in the correct position. That said the SC manifolds are more restrictive than the GS or LS so this effort definitely pays off.

I also plan on modifying the K&N FIPK for the GS400 and it should fit easily on an SC400



And the SAFC or Unichip to tune the fuel curve.

These mods on a GS400 have tested to over 280rwhp and 300rwtq which is like adding a 75hp shot of nitrous to a stocker :cool:

BTW, in excellent air my car posted 14.2 @ 99mph at Houston Raceway Park. It was traction limited and best 60ft was 2.19. If I had LSD and drag radials it would have posted a very low 14 and probably a 13.9 almost stock. My GTech meter posted 225rwhp which is probably 10-15hp lower than it would have dyno'd on a Dynojet.

With the above mods in the same conditions it would/should go mid 13s at 102-105mph WITHOUT nitrous. If you did the same and added the nitrous I believe a 12.9 @ 110mph is well within reason for a WELL driven car.
 
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scfou

New Member
Messages
53
Location
West Side
Very nice! That's exactly what I plan on doing, to extract as much power out of the stock V8 before I run a safe 75 shot of nitrous. I already have the BFI mod done last week and a custom exhaust system. The BFI mod really gives you power that you can feel, and it's much more torque-ey in the high end. I will need to switch my exhaust design back to a "Y" or "X" setup though, because the current "H" setup is throwing a CEL. My next step will be the headers and then definitely a safc to tune it up big time, and finally, a 75 shot of ZEX and I should be good to go. For some reason it seems like basic mods on V8's really make a huge difference compared to mods on 4 or 6cyl. I definitely won't need to run a super charger or turbo on this bad boy, and I'm happy about that.
 

sungphil

New Member
Messages
5
Location
Santo Domingo
1uz vvti custom exhaust, w58 tranny and afc neo

For now I got rid of OEM exhaust and made a custom 2.5 Y exhaust and 3'
W58 MT Tranny and a AFC NEO tuning
Right now the car have 278 WHP and 298 Torq
Right now with radial tires and no tuning whats so ever the car made
14 sec flat in 1/4 miles
It didn't let me go any faster because of the tire squeering...
Fotgot to tell you I have the 1uzfe VVTI in a Toyota Altezza (is300)

Coming soon
Ported head
Modified Intake Manifold
Header
AFC NEO Tuning
I Will post the results of it

I would love to upload some pics but don't know how
 
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