1UZ Rods

[Lextreme II]

I just opened up a 1995 SC400 and discovered that the 1995 has skinny rods. Initially my impression was 1996 and up and it went as low as 1995. Here are some pictures. The second picture you see is a bended rod from a 8-9 psi single turbo.

 

[stevechumo]

Whooh..whooh! That looks crazy. Do you have the pre-95 rod so we could compare? I'm sure the demand for the pre-95 engine will go up after this.

 

[Lextreme II]

Here you go... http://www.lextreme.com/Toyota-Lexus-Rods.html

 

[JBrady]

This is what I expected. Lexus redesigned the 1uzfe for the 1995 LS400. One confusing aspect is that while the LS400 gained 10hp and 10tq rating for 1995 with this upgrade the SC400 did not get a change and remained at 250hp and 260tq.

Now, I have not had a chance to thoroughly investigate the 1995 SC400 so here is a chance to do so.

Changes in the 1995 LS400 included higher compression from 10.0 to 1 to 10.4 to 1. Does anyone have the OFFICIAL factory compression rating for a 1995 SC400???

Compression, slight camshaft changes and dual tube exhaust manifolds for the LS400 were included with lighter pistons, rods and crankshaft. I have argued that the original rating of 250hp/260tq was an OVER-RATING by Lexus and should be more like 230hp and that the 260hp/270tq of the 1995-1997 LS400 is accurate. This is supported both by dyno readings (175rwhp early, 200rwhp 1995-97) as well as performance improvements of over a second quicker in both 0-60 and 1/4 times.

The SC400 had single tube exhaust manifolds for all years from 1992-2000 and I believe are down about 10hp on the LS400 from 1995-2000.

Finding skinny rods in the 1995 SC400 suggests it may have also received the 1995 improvements seen in the LS400 but was rated lower because it is slightly lower due to the restriction in the exhaust manifolds.

Again, it would be nice to confirm what is the real deal with the 1995 SC400 engines.

 

[Tacoma_Kyle]

Well I may eventually be of help. I have a 95 SC400 engine. I even VIN verified it (still have the receipt) because I thought it was a 96 one and was bummed cause I didnt care about the rods, its stayin pretty much stock so 10hp more is good. There is a high likelihood that I will be modifying the oil pan some time. Maybe 2 weeks from now maybe 2 months, I dont know when. Whenever I feel like it. Mostly dependant on how cold it is and how bored I am.

My guess is the same as Jakes, LS400's got it first. SC400's the next year. I think another way to look at it is all OBD II engines have smaller rods. Well for UZ's anyhow...

But yeah when I eventually get to pulling the pan off (oh-so hard...) I can check with calipers and take some photo's.


EDIT: Further considering the topic, I side with the 95 SC400 1UZ being different from the 95 LS400. Why? THey use different AFM's. My 95 motor uses the older style aluminum one. I have a hotwire from a 95-97 LS400 and it uses a smaller connector. Usually renovations are all at ocne in cars rather than partial piecing.

 

[Pro]

see, i thought the EARLY engines got the 10.4:1 CR, and the later engines (post 94) got the 10.0:1 CR.

 

[Zuffen]

I can't imagine Toyota building two versions of the 1UZ (given they were a numerically low output engine) at the same time.

I belive they would be the same internals with only the sumps and accessories varying.

 

[Lextreme II]

I think Toyota made the 1uzfe from 1989 to 1994 is the same and change slightly from 1995 on. So in another word, 1990-1994 LS400 would be same as 92-94 SC400. In 1995 LS400 got OBDII and a later SC400 also got OBDII. So after opening my friend's engine we can confirm that 1995 SC400 has skinny rods.

 

[stevechumo]

I think the pre 95 is better for boost, but the post 95 is better for NA applications. So start with the right engine.

 

[drifty325i]

I think the pre 95 is better for boost, but the post 95 is better for NA applications. So start with the right engine.

I Agree

But i also think the late 1uz can handle low boost with out a problem, 5-7lb if tuned correctly

 

[JBrady]

The problem is that David aka Lextreme has confirmed that at least ONE 1995 SC400 has the "late" "skinny" rods. Unfortunately that does NOT guarantee anything.

It is possible that:

1) Only the rods were changed on an otherwise carry over engine for the 1995 SC400. Since the engineering was done to make the upgrades or changes to the LS400 and part of that was a new rod design it is more than reasonable to suggest that those rods would be spec'd for all engines. So, skinny rods do not confirm the other mods found in the LS400.

2) Existing stock of 1UZFE engines were used up in the SC400 for 1995. This could be the case and if the supply was exhausted before the 1995 production was completed the "new" engines could be used on the remainder of 1995 SC400's. This would create some 1995 SC400's with the old engines and some with the new engines. Thereby if one example is dissasembled and checked it would not assure that all 1995 SC400s shared the same engine.

3) If number 2 above is correct it is possible that some 1996 SC400s received the "old" engines IF the goal was to exhaust supply AND the supply was not exhausted in the 1995 run. I don't believe there are any obvious external differences except for possibly the engine cover which would probably fit the old engine.

4) ALL 1995 SC400s got the upgraded engine and were rated accurately at 250hp/260tq which is 10hp/10tq less than the accurately rated LS400 which got better exhaust manifolds. This would look like no changes were made but in fact were made. Again, all of these are postulations and fall under the category of MAYBE unless and until confirmation could be made.

A GOOD way would be to dyno test any 1995 SC400. If it makes 190rwhp or so it should be the NEW engine and if it makes 175rwhp or so the OLD engine. Of course the above variables still exist.

It would also be GOOD to test the camshafts from known old and new engines as the camshaft timing was slightly increased. Like peak power numbers absolute cam numbers like max lift and total duration do not indicate cam lobe profile which can vary considerably while keeping peak numbers identical. We do know that the 1995-1997 LS400 is considerably quicker and faster than the 1990-1994 LS400. Much quicker than the advertised 10hp gain can account for (more like 30hp). 4 tenths of compression doesnt make 30hp nor do better manifolds. Lighter internals with the others and tuning may be the only changes or maybe the heads are better as well? Questions, questions, questions.

 

[stevechumo]

It'll be nice to have an insider of Toyota Corp to confirm that.

 

[Tacoma_Kyle]

I can't imagine Toyota building two versions of the 1UZ (given they were a numerically low output engine) at the same time.

I belive they would be the same internals with only the sumps and accessories varying.

Well in 95 they release the Tacoma's with the 3.4's (5VZFE) and the 4runners still had the 3.slow (3VZE).

In 96 when the 4runner got redesigned THEN they got the 3.4.

Yeah it isnt the same exact engine but same family.

 

[Tacoma_Kyle]

Oh whoops---I thought you had a LS engine for some reason.

 

[Lexus94]

I know this is an old thread , But I have a 1994 UZZ32 and it has the smaller rods , I think mine was 8/94 or 11/94 and also 10.5:1 pistons . From what i know they went to the smaller rod in August of 1994 .

 

[spf_lexus]

I have argued that the original rating of 250hp/260tq was an OVER-RATING by Lexus and should be more like 230hp and that the 260hp/270tq of the 1995-1997 LS400 is accurate

What if the engine ratings were spot on and its the transmission thats causing the gap in rwhp? 175rwhp can also be viewed as 25% loss thru the transmission. Im pretty sure the 95+ came with the a650e 5-speed and this may be another reason for the whp difference. Revised cam profiles and 1/2 a CR point with lighter internals could make up for the extra 5% differencer in whp in my opinion. I just dont have enough info on the revised cam profile and the revised state of tune for the 95+ to give a solid answer.

 

[JBrady]

What if the engine ratings were spot on and its the transmission thats causing the gap in rwhp? 175rwhp can also be viewed as 25% loss thru the transmission. Im pretty sure the 95+ came with the a650e 5-speed and this may be another reason for the whp difference. Revised cam profiles and 1/2 a CR point with lighter internals could make up for the extra 5% differencer in whp in my opinion. I just dont have enough info on the revised cam profile and the revised state of tune for the 95+ to give a solid answer.

95-97 had the same A341E that the 90-94 used. These engines make about 25rwhp more than the 90-94. This is backed up in performance gains. I believe the originals made 250hp without cats or air cleaner assemblies and tuned for 93 octane. I say this based on dyno pictures of the original engines. With cats, full exhaust, quiet air cleaner assemblies and tuned to tolerate a wider range of fuel quality the actual installed engines make right around 175rwhp. That would be a 30% power loss from 250. The 95 LS400 makes about 200rwhp. Same drivetrain including differential ratio 3.62. 30% off its 260 rating would give 182rwhp. 260hp - 23% loss = 200rwhp. 250hp - 23% loss = 193rwhp. 225hp - 23% = 173rwhp. With simple exhaust upgrades, intake upgrades and tuning the early engines often make over 200rwhp. Cam differences are marginal. Compression helps but is also marginal. This is the basis for my belief of the actual install output of the original 1uz at 225-230hp.

On the 1998-2000 GS400s rated at 300hp with the A650E 5 speed the typical dyno measures 235rwhp = 22% loss. Pretty consistent with the other models we are looking at here.

Regarding the SC400 with the 96-97 engine it still had the single tube exhaust manifolds while the LS400 got the dual tube tri-y type in 95-97 giving it a reasonable 10hp edge over the SC400s which carried through the 98-00 engines as well. GS400 was 300hp (accurate), LS400 290hp (accurate) SC400 290hp (10hp optimistic)(typical 98 LS is even to a SC400 even though the SC is slightly lighter).

The bigger news for this thread is the report of the skinny rods on the 94 model. This is concerning for anyone running boost on a 94 engine assuming the stronger rods. As usual more data will help here and the skinny rods change over actual dates and market areas would be helpful.