YODAONE

It is unclear how exactly Toyota measures HP and Torque...but it is fair to say they are not using rear wheel figures...but flywheel are using 100% gasoline (not gasahol)......

On information window sticker EPA mileage figures are derived using 100% gasoline (more heat content and thus better mileage)

I have read 15% loss as well, but attributed that to vehicles equipped with manual, not automatic transmissions....

Automtic transmissions are enegy hogs so the dyno figures are unsurprising..

The two "before" dyno runs were very similar and were posted separately, and as overlay.

There are a few warbles in the curve, but consistently so...

I unterstand the ACIS opens the short intake runners at 4,000 RPM...these figures.are over 4,000.....

The chassis dyno technician commented that torque and hp ratings are not measureable on automaric transmissions at lower RPMs...

The constant here is the same dyno was used for before and after testing.

The results are consistent with the seat of the pants feel...it is much faster across the RPM range.

I will share an irritating result that I noticed two days ago...in rainy conditions the wheels spin much easier when accelerating from a stop therby triggering the anti-slip...

I have to go much lighter on the gas pedal to avoid this result.

The engine runs well, has fresh spark plugs (for before test) does not consume a drop of oil (I use more oil wiping the dipstick each time I check it)

I reused all of the same ACIS components from the original intake...

Original gaskets were not leaking, but replaced them.

You are certainly welcome to dyno a 1998-2000 LS400 to see if your results vary.

Seems I am the only one with an Extrude-honed intake and.recommend another member step up.

Growing a little weary of comments questioning validity of chassis dyno and tangible performance improvements.

djamps

I'm not questioning the validity if your dyno charts or the fact that you had real gains due to the extrude hone, especially as shown above 5krpm. Please don't take offense. I'm very familiar with dynojets, their software (e/g winpep) and, have had other cars of mine on them dozens of times both auto and manual.

What I'm questioning the way your car was running on the original chart. You were way down on power below 5krpm for some reason because even with an automatic, I would considered 25% a worst case power loss between wheels and crank and the numbers still don't add up. Even this '93 SC400 (albeit modded), non-VTTi puts out more torque than yours did in it's stock tune, same dyno type and run conditions:
https://www.clublexus.com/forums/per...n-exhaust.html

But I will withdraw from this thread. At least until I can put my own LS on a dynojet.

YODAONE

Initially was not planning to chassis dyno but imagine what explaining improvements would be like then..

I thought the dyno figures were low too, but right or wrong, they are consistently right or wrong, with whatever improvement is depicted.

Someone in Chicago familiar with 1998-2000 LS400 want to go for a ride?

Not sure what else to do, unless someone else wants to Extrude Hone their intake.

YODAONE

Proper credit belongs to David Vizard...I posted a link to his editorial earlier in this post..These charts depict improvement in uniformity of airflow (CFM) on a Ford Mustang 302 intake... the runners are quite long , yet no where near as well engineered as Lexus ACIS intake manifold but felt merit mentuoning improvement in uniformity between runners...not to mention radiusing sharp edges inside the main intake chamber of ACIS...

The intaked air temperature reduction vs increased H.P. chart is from David Vizard, however this information presented is consistent and available online from numerous sources..

It is relevant from the standpoint the intake runners are no longer a rough casting = increased surface area, and now almost mirror smooth, thus less surface area (conservatively 50% less) so less heat is imparted into the intake charge= increased velocity and charge.

I noticed the 1998 LS400 lower Intake manifold to head gaskets incorporate an insulating barrier...thus very low tightening torque is recommended. So that is something Lexus determined would reduce heat transmission from cylinder head into intke manifold..

The extrude hone process takes that a step further by isolating heat via reduction in surface area.

So we have reduction of heat imparted into inake stream, less turbulence from temperature differential (perhaps analogous with exhaust pipe heat shields used to reduce temperature differential induced turbulence...however there the temperature differential is considerable)

The second benefit is the airflow no longer snags on the rough casting flash, casting seams, and casting mold injection points.. (not sure if "mold" is the correct term...not plastic I know), so performance improvements across entire RPM range...better laminar flow. Found this published torque curve comparing 1997 LS400 with 1998 LS400..

Again, not sure how thes figures are derived...but they cannot be rear wheel horsepower....
I did not use the ECT power switch or turn off the VSC....the dyno tech just pushed on accelerator pedal.

A side view of 1997 vs 1998 LS400 cylinder head..The 1998 intake port is considerably more efficient...However, I am contemplating extrude honing process of the exhaust ports to reduce surface area , thus reducing exhaust gas heat imparted into the aluminum cylinder head. Probably will follow up with secondary thermal barrier coatings. Expect 20-30 rear wheel horsepower gain (less heat means less propensity to trigger knock sensors thus iECU will maintain greater ignition advance across the curve)

YODAONE

The dyno operator mentioned the same thing.

I will need to verify all vacuum hoses, gaskets and seals for integrity.

The fuel pressure regulator is original and is a primary suspect.

The fuel pump and fuel pump resistor are original

The airflow sensor is original.

The OCV's are original and probably not 100%...the pintles or the bores are probably worn

The fuel injectors are original.and probably would respond well to inspection and thorough cleaning.

A minor exhaust manifold gasket leak is a possibility too...perhaps O2 sensors compensating by enriching mixture.

However, no trouble codes so am contemplating having Lexus performn a diagnosis...1/2 hour to an hour...

As far as I can tell the valve lash has never been adjusted.

djamps

It's normal to be running rich on stock ECU's without any tuning. They engineered it this way on purpose since no two engines are exactly the same VE (volumentric efficiency) and they put the mixture purposely rich to account for the edge cases -- too rich is way safer than too lean. You will need some ECU tuning (piggyback ECU since our lexus ECU's aren't re-programmable) on a dyno in order to get the mixture ideal at WOT.

YODAONE

Nothing is easy on this engine when it comes to modifications...or demonstrating improvements.

Am unsure whether a piggyback ECU is available and, or, compatible...

Happily, this appears to be more of a wide open throttle issue.

One thing no longer occurs at wide open throttle... whiteish smoke from exhaust. Visible .unburnt fuel..(not burning oil or coolant)

I know this ECU will compensate over-rich to prevent detonation...and so will determine whether another cause for over-enrichment...

I will replace the fuel pressure regulator and fuel pump (based on mileage, I choose to be proactive) and check for exhaust leaks.

The dealer has necessary equipment to determine engine fuel trim, ignition, and what various engine sensors are reporting.

Anyone replace knock sensors without a trouble code and discern improvement?
Not sure if these degrade with use and over time..

I will also work things from the thermal management side to further decrease intake charge temperature and increase density of intake charge..hope the ECU doesn't respond by enrichening mixture further.
The plastic ram air inlet atop the radiator (and forms top side of shroud/ducting) is absorbing heat...an easy fix with insulating medium.

peterls

Resurrecting an old thread to answer the last question: I have replaced knock sensors without really needing to (my starter died and I did not want to have to go in there ever again, even if someone else was doing the work) and it gave no noticeable improvement in performance. From what I gather, knock sensors just sit there waiting for a possible knock - and if they detect it, something is done with the engine management (retarded timing, I imagine). If everything is running as it should, they make no difference as they don't have much to do anyway, and my experience has been exactly that.

peterls

BTW, awesome work with honing the intake! Since fluid dynamics is something I work with, I will say that it is VERY easy to underestimate the importance of a fluid flowing with and without friction (read up on "inviscid flow" if you want to know more). I'll give an example to better illustrate the point: airplane falling out of the sky due to a tiny layer of ice on the wings, which completely ruins the air-flow and therefore lift of the wings. Fokker F28 Fellowship I think is notorious for that type of a problem and is/was mostly used in warmer climates once they figured how easily ice formed on its wings. A few millimeters of ice which is just a little less smooth than the wing and the airplane goes down. There was an accident with that type of an airplane and if memory serves me, they went down seconds after take-off, meaning - the fluid (air) does not even have to travel over the rough surface at a high speed for the trouble to become apparent (I believe that the typical take-off speed is around 140-150mph, give or take).

bradland

Just another piece of the checks and balances "Symphony" if you will...
"Knock" may not be the ideal term as the sensor picks up on knocks and pinging of detonation etc long before the human ear hears a knock. They are definitely active and necessary.

peterls

No doubt that they are necessary, I just didn't notice much of a difference... but then, the old ones were probably just as good as the new ones. (good to hear that they listen to everything, not just an audible knock or misfire.)

YODAONE

An update, and response to djamps comments...
Before embarking on transplanting a 3UZ-FE engine (LS430) into my LS400 removed my 1UZ-FE cylinder heads and had them surveyed by FX Engine Builders in Mokena. Professional.engine shop, more like an engine laboratory with all the tools. Very clean and organized.

The heads were disassembled and ultrasonically cleaned.
ZERO wear on valves, guides, or camshaft lobes. The engine builder had never seen anything like it before.
Aside from great design, the low wear is attributable to the timing belt damping crankshaft torsional vibration and isolating valvetrain harmonics.

However.after 175,000 miles and 20 years..the valve springs were tired, thus out of spec...and correct replacements are no longer available from Toyota.

The engine builder advised that there was evidence that the coils had been touching or binding(?)

So if the valve springs are tired then it is possible lack of valve control or minor valve float

This might explain flat readings or skewed results at upper RPM's.

To be sure, the seat of the pants feel.was there, but fresh valve springs would have produced better before and after dyno results.

It would be helpful if a valve spring manufacturer offered spring pressure slightly above stock.

All I was able to locate were aftermarkets that were literally double OEM spring pressure.
Not running at 10,000 RPM here.

Striker223

Does the extrude hone shop still have the tooling for this in hand to your knowledge Yoda? I'm going to have this done as well as long tubes soon

Also I'm going to be visiting family at Tinley park and I would be very interested in meeting you and your 400 since you likely have a near perfect example of the type. I'm also very curious to feel the difference in power that our mechanical changes have provided in person vs my as of now purely electronic ones.

YODAONE

P.M. your travel schedule.

YODAONE

Located a post on Lextreme discussing performance benefits of lower charge temperature.(smooth intake runners - thermal management)

Not a fan of plastic manifolds, but a considerable weight saving and validates availablity of improved performance on intake side:

https://www.lextreme.com/forums/inde...n-gs400.17321/

"2UZ plastic intake successfully installed on GS400"

Excerpts:

"So my ACIS solenoid died, and the intake manifold had to come off... So I figured, why not buy the plastic 2UZ intake from badblackgs and see what happens when I install it? From his experiments with it, he noticed a decent increase in torque. Plus the plastic keeps the air temperature down and is way lighter to lift off the engine when doing the starter. He sold it to me with a full set of fresh injectors, which was (initially) more cost-effective than having my injectors cleaned and balanced. The injectors from the 2UZ up to 2002 are plug and play in the GS400 harness and fit the 05+ intake manifold perfectly.

In order to keep the surgery minimally invasive, I tried my hand at making an adaptor to bolt the throttle body on to the intake using some eBay aluminum plates and some bolts from Ace Hardware. The cost started climbing from there, since I needed a 3-inch hole saw to cut the throttle body bore, and the metric bolts were pricey.

The adaptor worked though, so I test fitted everything. I planned on just using the 2UZ fuel rail, but the GS400 fuel line has the part that goes across the manifold integrated into the feed line. So I had to use the driver's side rail from the 2UZ, plug the hole at the other end, and use the passenger side rail from the GS400.

At this point, the two mistakes I made were not putting new upper seals on the fuel injectors and stretching the smaller of the two coolant lines to the TB because the whole TB was moved forward. The injectors leaked gas everywhere the next morning when I tried to go to work, and the coolant line popped later that night after I replaced the injector seals. #rookiemistakes

At this point though, everything is fine. The manifold bolted right to the engine, the vacuum lines all hooked up, and I was able to adapt the bracket for the throttle cable, even though the 2UZ manifold doesn't have a place to mount a throttle cable because the 03 and up are all 100% drive by wire. I relocated the vacuum canister and solenoid for the ACIS so I could access them without removing the manifold. Also installed a new solenoid, and the ACIS is working properly.

How does it drive? It definitely pulls harder through the mid RPMs, and the top end feels like it breathes easier. This car really moves.

I haven't had much time to really get familiar with it, but so far I'm thinking it's not a big enough gain to justify the pain of the install. Fabbing the adaptor took a lot of time, and as always when taking stuff apart there's the risk of breaking other stuff. At the very least, I know all those parts are fresh and working properly now."


"This has to be the best street car upgrade. More power, less weight, no downside. The aluminum intake is so heavy. I’ll bet the high rpm power is largely because of the cooler intake charge."

"Then tonight I goosed it to get through a yellow light and HOLY FRIJOLES I've never felt that car move so fast. Not even half throttle and the VSC almost had to step in. Now I truly feel like it was worth the time and money. That was the first time that car has ever really got me thinking "oh that's exciting!"