sc400 X-pipe and stock mufflers

brawls43

Member
Its great to find some good tech help finally. I originally found club lexus, but they seem more interested in hella flush and 20's. And other advice was more aftermarket part based, there seems to be more DIY here.
 

spf_lexus

New Member
I originally found club lexus, but they seem more interested in hella flush and 20's
haha, big time! I only use CL for wheel & tire fitments. I like Lextreme because its civil, to the point and like you said, more DIY oriented. 90% of the engine experience on their forum comes from 2JZ backgrounds so for someone modding a 1UZ, its like being in a foreign country.
 

brawls43

Member
...the engine experience on their forum comes from 2JZ backgrounds so for someone modding a 1UZ, its like being in a foreign country.
Very much so! I swear I asked for engine pointers right away and half the recommendations were to swap a 2JZ and turbo.
 

Spinnetti

Member
I appreciate the help, I'll see if I can ask JBrady some more questions. As an engineer, I tend to ask a lot of questions, and seeing data helps. If there's dyno charts of with and without cats, it'd be cool to see.
As an engineer, buy this book: "scientific design of intake and exhaust" - I think that's the name. For a fee burns stainless will do the analysis fir you too- they are top shelf. I've studied it extensively and there us a lot to know.
 

Launch

New Member
I like the CL site aside from the slam fest they have going with some of the newer guys that are just trying to learn. Like I said I've been building and racing cars for over 20 years and still got some grief simply because I asked some questions regarding the 1UZ being as this is a new project for me and it's a far cry from a supra. Besides I didn't really to many guys on there that could even put a car in the low 10's much less get into the 9's. Looks like this is a little mature site which is quite refreshing. Glad I decided to check it out.
 

spf_lexus

New Member
Welcome Launch!

You found the right forum if your even considering a UZ swap/build. You wont find flaming and heated arguements on here. Its a straight to the point forum.
 

Launch

New Member
Not swapping. I recently purchased a 79k original mi sc400. I have always loved the look and ride of these cars and I spent quite a bit of time to find one this clean. The sad part is that it is not much on power. Even for a DD it needs more power. not looking to put this into the 10's just pick it up a bit. I will be starting with the exhaust and going from there. How far is yet to be determined. But I do love driving this car so it will be a fun project.
 

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spf_lexus

New Member
Nice find. White is timeless. Our Exhaust section has several threads on N/A and F/I exhaust setups with plenty of info and specifics. Generally if your not planning a turbo or supercharger, a mandrel 2.25" system starting AFTER the front cats and Y pipe yield the best gains overall.
 

Spinnetti

Member
Pick up a 4.27 diff from a SC300 auto. Its a fast and easy swap for your car and will really liven up the off the line pickup. I'm just putting one in my 400 now (but had to make new front diff mounts)...
 

spf_lexus

New Member
Spinnetti, I know your speedo is a bit off from the final drive but can you estimate what rpm your seeing at 75mph? My SC400 has a slightly shorter 4th gear so im seeing 3,000rpm at 75mph. Maybe 2800 on the LS?
 

Spinnetti

Member
Spinnetti, I know your speedo is a bit off from the final drive but can you estimate what rpm your seeing at 75mph? My SC400 has a slightly shorter 4th gear so im seeing 3,000rpm at 75mph. Maybe 2800 on the LS?

Well, the speedo is tied to the RPM, so regardless of final drive it will read the same relatively - its just going slower than it "thinks" it is. You could compare the stock specs.... The LS400 has a 3.62 and the SC400 has a 3.92, so if my "maths" are right, the SC should run about 7% more RPM for a given speed than the LS assuming trans and tire diameter etc are the same. I went up to the 4.27 from the SC300 (and run shorter tires), which should give me about 15% more RPM for a given speed (but the speedo should read the same as it did before for a given RPM!). I did this because the car lugs out of the slow corners (or shifts to first and wails - either stinks), and shifts to 3rd right about when I need to slow down from fast straights... The revised gearing should get me out of the corners a lot harder and make best use of second, and use the "meat" of third for the fast bits....
 

spf_lexus

New Member
good info, thanks. This is funny but now I understand why I got a speeding ticket a few months back. I was clocked going 95 in a 75! I was judging my speed based on the transmission speed sensor so I was assuming I was around 85mph but now knowing that I was genuinely doing that speed, i'll lay off the gas from now on. I have been told the trans will tell the ecu a different speed so my top speed is cut a bit short but im wondering ig I can trick the VSS with a resistor to squeeze out some extra top end.
 

Spinnetti

Member
good info, thanks. This is funny but now I understand why I got a speeding ticket a few months back. I was clocked going 95 in a 75! I was judging my speed based on the transmission speed sensor so I was assuming I was around 85mph but now knowing that I was genuinely doing that speed, i'll lay off the gas from now on. I have been told the trans will tell the ecu a different speed so my top speed is cut a bit short but im wondering ig I can trick the VSS with a resistor to squeeze out some extra top end.
Well, the car doesn't know how fast its going. I calculates it based on RPM at the output of the transmission. That way, doesn't matter what gear you are in, or what the RPM of the engine is - it "knows" what the speed is based on the assumed tire diameter and rear axle ratio x the drive shaft RPM. As you go "bigger" in rear gear, it will actually read that you are going faster than you really are. Conversely, if you put taller tires than the stockers or a lower rear axle ratio, you will be going faster than it reads. So, if you want to be safe, put the SC300 rear in and you will read about 10mph fast ;)
 

Spinnetti

Member
Dang! Why can't we edit our posts! Anyway, with the "bigger" 4.27 rear end, you should have been going SLOWER than indicated, not faster.... mystery there.
 

spf_lexus

New Member
you should have been going SLOWER than indicated, not faster.... mystery there.
Thats what i assumed. I want to try swapping an sc300 speed sensor to hopefully re-calibrate. I feel ya on the posting edits... we used to have a 5 minute grace period but ever since the forum was hacked, we lost the privelage.
 

vince9164

New Member
How would the SC4 sound if it was straight piped w/ 2.25 from the center cat back? I don't want anything raspy on low and high rpms. Also are there any gains?
 

spf_lexus

New Member
Plenty of gains to be had with a 2.25". If you decide to straight pipe it, I would strongly advise using an X-pipe. It cancels out the raspiness your talking about and also produces more power under the curve. A lot of people think that because the UZ is a v8, it should ave a massive dual 2.5" system but this is totally false. unless your turbo'd or SC'd with lots of boost, you'll never ned to go that big... doing so while naturally aspirated will kill any kind of fun you'll have on the street. 2.25" dual = 400WHP support. Hope this helps.
 
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