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V8, 2 stroke poppet valve Lexus 1UZ engine

V8, 2 stroke poppet valve Lexus 1UZ engine

V8, 2 stroke poppet valve Lexus 1UZ engine

(OP)
Has any one got any experiance with two stroke poppet valve engines that they would like to share. I have built a Lexus 1uz V8 which is running as a two stroke. This project is primerily for increasing the volumetric efficiency for racing purposes. Any comments will be apreciated.

RE: V8, 2 stroke poppet valve Lexus 1UZ engine

I am aware of Toyota and Kawasaki playing around with this concept. I have never seen nor heard one run. If that engine you've shown in the photo runs, show us!

I would expect efficiency to be very poor unless direct-injection was used, which the engine that you have, does not appear to have. It doesn't appear to be even remotely possible to stop a lot of the fresh charge from short-circuiting out the exhaust valves.

I would expect valvetrain acceleration to be a severe RPM-limiting issue given that the valves need to open and shut within roughly half the number of crank degrees.

RE: V8, 2 stroke poppet valve Lexus 1UZ engine

Two stroke motorcycle engines in the 1970s produced very high HP but werent that easy to ride and had absolutely horrendous fuel efficiencies ie high fuel consumption. Might not be a serious objection when racing but something to be aware of.

RE: V8, 2 stroke poppet valve Lexus 1UZ engine

(OP)
Hi Brian, the engine can be seen running on facebook. You are correct in saying that the valve timing is half the duration as it previously was but it is force feed now. The short circuiting is not an issue, this is only for racing where fuel consumption is of no consequense. I have not run the engine under load as yet but getting 7500 rpm instantly is not one of my problems.

RE: V8, 2 stroke poppet valve Lexus 1UZ engine

Could you share a link to a video?

RE: V8, 2 stroke poppet valve Lexus 1UZ engine

(OP)
Engine video: ian.crawford.100 Facebook/Posts sept 2014

RE: V8, 2 stroke poppet valve Lexus 1UZ engine

Sounds awesome - even with no load.

Can you share valve timing and/or valve lift with us?

je suis charlie

RE: V8, 2 stroke poppet valve Lexus 1UZ engine

Where did you see the video? I don't have a link.

Oh, I figured it out. Dang, no Facebook ☹️

RE: V8, 2 stroke poppet valve Lexus 1UZ engine

(OP)
Ex opens 90 BBDC, Ex closes 25 ABDC, Inlet opens 25 BBDC, Inlet closes 90 BTDC. Cam and crank belt gears are 40 teeth using stock belt (stock gears are 24 for crank and 48 for cams). The engine is basicaly stock apart from the camshafts, Bullit blower manifold and the ignition and fuel ECU. The ECU is Spitronics with wasted spark for ignition and fuel triggers using batch injection. Blower overdrive is 20%.

RE: V8, 2 stroke poppet valve Lexus 1UZ engine

I have facebook, but the cryptic information about the engine video leads me nowhere. Proper link to it?

From the cam timing, it looks like the idea is to let the exhaust blow down and perhaps even pull a slight vacuum on the cylinder with only relatively slight overlap between IVO and EVC, then blow in most of the fresh charge afterward, thus cutting down on the wasted scavenging. There's going to be a fair bit of residual exhaust in the cylinder; oh well.

RE: V8, 2 stroke poppet valve Lexus 1UZ engine

(OP)
Brian, really, what part of the "cryptic" link don't you understand? Is it Facebook or is it ian.crawford.100 or is it "Posts Sept 2014"? Please let me know so that I can help you.

RE: V8, 2 stroke poppet valve Lexus 1UZ engine

Anyone not having a facebook account can hardly ever see anything posted to facebook. It's part of what makes it an effective marketing tool for advertising - users are essentially forced to opt in to see anything there. Even with a direct link the first mouse touch causes the screen to be covered with a "Sign in" pop up.

RE: V8, 2 stroke poppet valve Lexus 1UZ engine

Thank you!

Keep us updated on this... thing you have done.

RE: V8, 2 stroke poppet valve Lexus 1UZ engine

Wow - That sounds surprisingly smooth, very unlike a normal (carbureted and loop-scavenged) two-stroke! It's sure a screamer!

With a normal (4-stroke) V8 crankshaft, it's going to have a simultaneous-double-fire firing order.

Good job for making it happen!

RE: V8, 2 stroke poppet valve Lexus 1UZ engine

Cool project.
You mentioned waste spark, but I don't get it, if it's double fire. Or do you have waste spark happening at BDC?
One pitfall to think about; the crank has not been validated for double fire and the rpm may be a torsional vibration challenge as well. Be prepared for some learning when you get some load behind it.

"Schiefgehen wird, was schiefgehen kann" - das Murphygesetz

RE: V8, 2 stroke poppet valve Lexus 1UZ engine

There are several SAE papers on this topic and configuration. It is worth reading up on the Ricardo "Flagship" concept in papers 900802 and 920778. There is a lot of information of scavenging of such an engine in 1999-01-1250.

RE: V8, 2 stroke poppet valve Lexus 1UZ engine

(OP)
The wasted spark is as in 4 stroke configuration but is used to fire the oposite cylinder at TDC to crate the double firing. Like wise the injectors can be set to "two stroke" to fuel the opposite cylinder. The injector setting was not intended to be used this way but rather to supply more fuel for engines that are running injectors that are too small to supply the rquired amount of fuel, for instance if you change from gasoline to methanol. I will attach the wiring diagram and ECU setup instructions. What Lou and PJGD have said is usefull information and it is this that I am looking for.
So far so good, the engine is super responsive on gasoline but what about methanol or even nitro. The purpose of this project is obviously to get more power out of the engine, but rather than going the conventional route as a 4 stroke with big cams, heads and valves, give it twice as manny power strokes in a given time without the drawbacks of of a narrow powerband.
Brian mentioned that the engine runs very smooth. This is true and supprisingly it is simmilar to a Detroit 6-71 or 8V-71 at idle.

RE: V8, 2 stroke poppet valve Lexus 1UZ engine

Even though the waste spark will deliver a spark to the cylinder at the right time, there is a big difference in the 2, in terms of spark requirements.
The waste spark is only firing 1 cylinder under compression at a time. The other cylinder is not, and takes a significant less amount of voltage to jump the spark gap. So you have 1 cylinder that requires high voltage, one that doesn't. This also means that most of the energy will go to the cylinder that is firing.

With the 2 stroke, they will both be in compression at the time of spark, and so you will have 2 cylinders that require high voltage each time. So you need to generate higher voltage, and the energy will be roughly split between the 2 cylinders.

If your existing system is strong enough, it's not a problem. Usually OE ignitions and coils can provide voltage well in excess of the amount they need. But if you start to experience misfires or coil failures, this could be something to look at. Especially if you crank up boost or do something that will require more spark voltage per cylinder.

Coils can be rated for 30kV-65kV(typical ranges I've seen), and this has mostly to do with epoxy, and methods of winding to limit voltage jump between turns of the coil. Running 2 single output coils in place of the dual output coil, with the primaries in series, would be a way to fix this if it seems like coils are failing

Adding a CDI could give you a bump in voltage if you start seeing misfires. Plus those use the original signal just as a trigger, so if your engine is accelerating too quickly for the ECU dwell calcs to correct, that should take care of that problem.

RE: V8, 2 stroke poppet valve Lexus 1UZ engine

Good point bradrs. I will add that although total voltage output of the coil needs to be almost double the requirement for "waste spark" operation, insulation should not be a problem. Although coil output voltage is almost double, one plug sees positive voltage and the other negative. Therefore each HT lead will only see the voltage level it sees when "firing" a plug in waste spark mode.

je suis charlie

RE: V8, 2 stroke poppet valve Lexus 1UZ engine

I agree gruntguru, the HT should be OK. I was more concerned with the windings in the secondary(output side) of the coil. They will be producing potentially close to double the voltage. And depending on how the coil windings are done, that could be a problem. It could increase the voltage between neighboring turns in the coil, making it easier to burn through coating or epoxy. A split bobbin which divides the windings into sections helps with that, but you'd probably need to slice a coil to see if that is the case. I'd just call it something to keep in mind, if you run into ignition issues.

RE: V8, 2 stroke poppet valve Lexus 1UZ engine

Letlhakane, I shared your video in the "All sorts of multi cylinder engines" group on Facebook, and a sharp viewer noticed the video is sped up during the reving sequences by watching your hand at the end of the clip. Is he right?

RE: V8, 2 stroke poppet valve Lexus 1UZ engine

It looks sped up. Has it been on a dynamometer yet? I guess it has a strange sort of loop charging effect, I always wanted to try that, sure would like to see how the HP compares to the 4 stroke version.

RE: V8, 2 stroke poppet valve Lexus 1UZ engine

Just ocurred to me that the chamber design could be usefully improved in line with the needs of a two stroke.

Firstly - typical pent-roof tumble works against you here. The first thing encountered by much of the intake flow is - the open exhaust valves - short circuiting the scavenge process. Reverse tumble would be preferrable - perhaps a wide valve angle with vertical intake port between the valves.

Secondly - the valves are always closed at TDC so the piston crown can be fitted much closer to the valves (no valve reliefs) with a small chamber concentrated around the spark plug.

je suis charlie

RE: V8, 2 stroke poppet valve Lexus 1UZ engine

(OP)
In reply to rodrico's statement about a sharp observer noticing some thing untoward about the video clip I can only say this: I took the video my self with a Nokia N8 phone in one hand and operating the engine with the other. The video has not been edited,tampered with or otherwise modified in any way, it was simply downloaded from the phone then uploaded to FB from there it was downloaded and uploaded to this forum.

RE: V8, 2 stroke poppet valve Lexus 1UZ engine

Doesn't look sped up to me, just quick hand motions. This engine is going to sound like it is spinning faster than it is. Each exhaust manifold will have 4 pulses per revolution discharged from it, evenly-spaced on each bank. It won't have the once-every-two-revolutions superimposed frequency that a normal 4-stroke V8 has because of its irregular firing pattern into each exhaust manifold. No "V8 rumble".

Detroit Diesels were nicknamed "screaming Jimmy" for much the same reason. They sound like they're spinning much faster than they actually are.

RE: V8, 2 stroke poppet valve Lexus 1UZ engine

Quote (Letlhakane)

In reply to rodrico's statement about a sharp observer noticing some thing untoward about the video clip I can only say this: I took the video my self with a Nokia N8 phone in one hand and operating the engine with the other. The video has not been edited, tampered with or otherwise modified in any way, it was simply downloaded from the phone then uploaded to FB from there it was downloaded and uploaded to this forum.

I meant no offense. I was simply reporting what many said and asked you to clarify one way or the other.
I told folks I didn't think it was sped up, but then someone pointed out the very last 7 seconds where your hand seems to move abnormally fast, and I became less sure.

The video of your engine I posted in the "All sorts of multi cylinder engines." group on Facebook now has 258 comments (many are repetitious because folks don't read all the prior comments before asking a question). Most comments are simple statements of awe. A surprising number are people saying "it can't be a two stroke because it has valves." Others have disabused them of the notion. You really should join the group!

RE: V8, 2 stroke poppet valve Lexus 1UZ engine

How about the HP figures? Power and torque curves?

RE: V8, 2 stroke poppet valve Lexus 1UZ engine

(OP)
There are no HP or torque figures available as I live in Botswana and as far as I am aware there are no dyno's available here. I would need to take it to South Africa to do this but realisticaly it would be much simpler to test it on a drag strip (also in South Africa)after this current Covid story is sorted.
The quick hand action, at the end of the video, clearly indicates how responsive the engine is and the possibility of over reving is very real.
bradrs has commented on the ignition system and it seems that he is far ahead of me on this subject. Originaly the engine had two coils and two distributers The distributers simply distributed the HT current to the varios cylinders, nothing else. Now I have installed four dual coils fired by four triggers and removed the distributers. The thinking was that this should be the same, or similar, as having eight coils. Would it be a better solution to go the "coil on plug" route?
gruntguru is suggesting that some of the fresh scavenging air is short circuited and passes out through the open exhaust valves. This is certainly correct and I am using a 6-71 blower instead something larger. The 6-71 blower is sufficient to charge a 7 liter (427CU) Detroit at 6 PSI with the blower spinning at crank X 2 so the thinking here was that this setup may be a "bit light on" with the blower turning at crank + 20% on a 4 liter engine. Having the inlet valves/ports in a more vertical possition would be beneficial but not possible for me to accomplish. Non rotating inlet valves with shrouds on the stem side facing the exhaust valves could also be a practical solution.
RodRico, I am waiting for a response for approval from "All sorts of multi cylinder engines" Thanks to you all for the suggestions!

RE: V8, 2 stroke poppet valve Lexus 1UZ engine

Maybe you've thought of this already: I see no need for a massive (e.g. stock) flywheel. You could probably get away with the lightest possible piece that can take the torque transfer to the clutch.
But, caution, considering the rpm you will reach - make sure whatever you use has the needed integrity.

"Schiefgehen wird, was schiefgehen kann" - das Murphygesetz

RE: V8, 2 stroke poppet valve Lexus 1UZ engine

(OP)
Lou, it will be using a stock torque converter

RE: V8, 2 stroke poppet valve Lexus 1UZ engine

I see.
Not my area of expertise, but is a stock converter well adapted for racing use? Coming to mind are items such as stall speed, torque capacity, and rpm capability.

"Schiefgehen wird, was schiefgehen kann" - das Murphygesetz

RE: V8, 2 stroke poppet valve Lexus 1UZ engine

7500 rpm isn't significantly over the base engine's normal speed range.

Stall speed is a function of torque and converter diameter. Advertised stall speeds are an estimate based on a lot of assumptions. This engine will likely have close to double the stall speed with the stock conveetrt.

RE: V8, 2 stroke poppet valve Lexus 1UZ engine

Quote (Letlhakane)

gruntguru is suggesting that some of the fresh scavenging air is short circuited and passes out through the open exhaust valves. This is certainly correct and I am using a 6-71 blower instead something larger. The 6-71 blower is sufficient to charge a 7 liter (427CU) Detroit at 6 PSI with the blower spinning at crank X 2 so the thinking here was that this setup may be a "bit light on" with the blower turning at crank + 20% on a 4 liter engine. Having the inlet valves/ports in a more vertical possition would be beneficial but not possible for me to accomplish. Non rotating inlet valves with shrouds on the stem side facing the exhaust valves could also be a practical solution.
I think a deflector welded into the combustion chamber would be better. Perhaps recess the exhaust valves into the head a little and add a "mound" around the perimeter nearest the intake valves.

je suis charlie

RE: V8, 2 stroke poppet valve Lexus 1UZ engine

(OP)
I like the idea of the welded in deflector as this can be customized in all possible ways to achieve the desired result without the risk of something breaking or falling off into the works. I will need to look for a set of heads to play with.

RE: V8, 2 stroke poppet valve Lexus 1UZ engine

Quote (Letlhakane)

I like the idea of the welded in deflector as this can be customized in all possible ways to achieve the desired result without the risk of something breaking or falling off into the works. I will need to look for a set of heads to play with.

You may not even have a significant problem. You're scavenging for a whopping 50 degrees then pressurizing the intake for 65 degrees and presumably firing the injectors shortly after exhaust closes, so you shouldn't have any direct transfer of fuel out the exhaust. That leaves spoiling of combustion due to excess EGR which is manifest as unburnt hydrocarbons in the exhaust (see https://x-engineer.org/automotive-engineering/inte... ). Here in the US we can get a reading on unburnt hydrocarbons at any emissions test site. Do you have emissions test facilities in Botswana, perhaps in the largest city? As long as you don't have excess oxygen or unburnt hydrocarbons in the exhaust, I believe you're getting maximum power out of your engine given the available airflow and compression ratio.

RE: V8, 2 stroke poppet valve Lexus 1UZ engine

(OP)
To be true full, I really don't know if there are any regulations here regarding motor vehicle emissions. Basically it seems if it runs okay, its good. So there is no testing of light motor vehicles after they have been first registered. Even when the car is secondhand and imported when they are first registered there are no emissions tests done .

RE: V8, 2 stroke poppet valve Lexus 1UZ engine

O2 sensors are easy enough to obtain. I wonder whether there's such a thing as a small unburnt hydrocarbon sensor.

RE: V8, 2 stroke poppet valve Lexus 1UZ engine

True, but don't confuse a lambda sensor as being a useful "O2 sensor". They measure lambda, not oxygen concentration.

je suis charlie

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