Prius engine conversion

[merccom]

Originally Posted by kurzer

as i sad, the simpel way is to keep trottle, injection and header etc. of the existing car and only go for the engine itself. what comes in and what comes out is pretty much the same in nowerdays. so if you can bolt this parts on, the engine will work.
2 points are to think of. how to drive the ignition (prius has coil on plug), and is the prius doing something with the camshaft.

with megasquirt driving the ignition and cams are non issues

[Ecky]

I've been thinking about this for a while... I believe the VTEC mechanism in Honda's R series puts the engine in Atkinson cycle when cruising, and changes back to Otto when idling or accelerating. It would surprise me if modern engines from other manufacturers didn't already do this.

It would probably be simpler to use one of these engines since they are already tasked for what you want, though you'll probably pay more for the engine. The only issue I see is, the smallest R- engine you can get in the states is 1.8L, which is more than overkill for the eco-minded. They have a 1.6L variant in Europe and Asia but you'd need to import one.

The only manual transmission Honda makes for the R18A is rather short, since they're marketing manuals as sportier.

You would see MPG gains over a 2006+ Civic so long as the vehicle you dropped it into was lighter or had a lower CdA, such as a CRX. It would also be beneficial to mate it to a longer transmission, like that found in the CRX HF.

I'd also definitely do some research to see if the ECU could be reprogrammed to increase the variety of conditions under which it goes into Atkinson cycle, and also whether you could map it for lean-burn. (The R-series fuel mappings are more focused on emissions)

[merccom]

Originally Posted by Ecky

I've been thinking about this for a while... I believe the VTEC mechanism in Honda's R series puts the engine in Atkinson cycle when cruising, and changes back to Otto when idling or accelerating. It would surprise me if modern engines from other manufacturers didn't already do this.

It would probably be simpler to use one of these engines since they are already tasked for what you want, though you'll probably pay more for the engine. The only issue I see is, the smallest R- engine you can get in the states is 1.8L, which is more than overkill for the eco-minded. They have a 1.6L variant in Europe and Asia but you'd need to import one.

The only manual transmission Honda makes for the R18A is rather short, since they're marketing manuals as sportier.

You would see MPG gains over a 2006+ Civic so long as the vehicle you dropped it into was lighter or had a lower CdA, such as a CRX. It would also be beneficial to mate it to a longer transmission, like that found in the CRX HF.

I'd also definitely do some research to see if the ECU could be reprogrammed to increase the variety of conditions under which it goes into Atkinson cycle, and also whether you could map it for lean-burn. (The R-series fuel mappings are more focused on emissions)

not really, while variable valve timeing is useful one of the main aspects of the atkinson cycle engine is extremely high static compression which no amount of valve timing is going to change (the prius engine runs 13.5/1 static compression)

as far as "lean burn" goes that really is a function of which o2 sensor you're useing. if you're running a wideband o2 sensor you can program any engine to run lean burn if you're running a standard o2 sensor you cant.

[Ken Fry]

Originally Posted by merccom

not really, while variable valve timeing is useful one of the main aspects of the atkinson cycle engine is extremely high static compression which no amount of valve timing is going to change (the prius engine runs 13.5/1 static compression)

I'm shaving a point pretty fine here, but I'm inclined to agree with Ecky. The central feature of the Atkinson cycle engine is the asymmetry of compression and expansion strokes. (The precise compression ratio number is less important in characterizing the cycle.) If the intake valve closes late enough to have significant blow back into the intake manifold (as described by Honda) then I think that qualifies as Atkinson cycle. In the Honda the effective compression ratio would be perhaps 8:1 while the expansion ratio would be 10.5:1.

Further supporting this interpretation is the fact that Honda says that manual throttle control would be effectively impossible, because the effect is so dramatic: the driver is applying very little throttle via the pedal, but the engine's throttle is near wide open. In most variable valve timing schemes manual throttle control is possible.

Finally, the Chevy Tahoe Hybrid engine is described as Atkinson cycle, with a geometric compression ratio of only 10.8.

[merccom]

Originally Posted by Ken Fry

I'm shaving a point pretty fine here, but I'm inclined to agree with Ecky. The central feature of the Atkinson cycle engine is the asymmetry of compression and expansion strokes. (The precise compression ratio number is less important in characterizing the cycle.) If the intake valve closes late enough to have significant blow back into the intake manifold (as described by Honda) then I think that qualifies as Atkinson cycle. In the Honda the effective compression ratio would be perhaps 8:1 while the expansion ratio would be 10.5:1.

Further supporting this interpretation is the fact that Honda says that manual throttle control would be effectively impossible, because the effect is so dramatic: the driver is applying very little throttle via the pedal, but the engine's throttle is near wide open. In most variable valve timing schemes manual throttle control is possible.

Finally, the Chevy Tahoe Hybrid engine is described as Atkinson cycle, with a geometric compression ratio of only 10.8.

Ok I will concede that yall are correct. I will say that the situation is not optimum however. If you have an engine that has 10/1 static compression when the cams retard and you go atkinson your dynamic compression could be in the 7/1 range which certainly would be no good for fuel mileage.

Another line of thought I've been going down is maybe ruNning standard otto cycle but at 12 or 13 compression and using water injection to control detination under load while keeping the advantages of increased compression under part throttle.

Just want to reiterate that of course vehicle optimazation comes first. But after that is done what can be done to build a better engine

[user removed]

Maybe something here is not understood. Atkinson cycle did not use variable valve timing. The offset crank is a means that accomplishes characteristics of Atkinson's design.

The change in valve timing which allow blow back into the intake manifold, combined with residual exhaust gas in the cylinder allows partial throttle positions with higher actual compression in the cylinders. This is done by having a higher actual compression ratio which is reduced by the actuation of the camshafts, with the fuel mixture diluted by higher percentages of exhaust gas in the combustion chamber when the piston is compressing the mixture.

Maybe not the best explanation but it is a "lean burn" scenario, without the NOX emissions issues of the classic lean burn design. Higher part throttle in cylinder compression, higher EGR content in the compressed mixture gives you the advantage of better "leverage" while using less fuel. The mixture will not heat up as high in combustion as a normal mixture but most of that is mitigated by the higher static compression.

To a certain degree this allows the throttle position to be more open for the same amount of power while power produced is lower due to higher EGR percentage and higher in cylinder compression.

With a static compression of 13.5 to 1 at 50% manifold vacuum that works out to 6.75 to 1, while a more typical 10 to 1 at 50% throttle would give you 5 to 1 actual compression (the amount of fuel & air actually compressed by the piston).

A normal engine idling with a static compression ratio of 10 to 1, with 22 inches of manifold vacuum at idle would produce 8/30 of the static compression. That's less than 3to 1 actual compression 80/30 to be exact, assuming atmospheric is 30 inches.

This is the direction most manufacturers are going to with super high compression ratios, Atkinson cycle, with one more critical improvement. Direct Injection, which the Prius engine does not have, allows fuel to be injected into the combustion chamber, but that is only part of it. Once you can inject fuel into the combustion chamber at pressures higher than the combustion temperature produces, then you can inject fuel any time after TDC, with no possibility of pre ignition. Mazda is doing this with SKYACTIV, with the last injection at something like 60% ATDC. This allows them to stretch out the combustion duration to produce a more even application of pressure to the top of the piston for greater efficiency, a longer push, in other words.

An engine swap from a Prius to another car, eliminating the hybrid components, while doable, would require some extraordinary capabilities, since the programming of the ECU depends on the hybrid synergy drive to cover specific portions of power application. It would be way beyond most peoples capabilities for probably not as great a benefit as might be imagined.

Get a manual Echo or Tercel and put one of the higher overall ratio Japanese home market transmissions in it and get 50+ MPG that way.

regards
Mech

[drmiller100]

another option is to go find a wrecked 1992 honda CX. 1500 cc's, high compression, lean burn, and the engine/trans combo is 300 pounds.

also, OBD1 with lots of aftermarket support for modding.

[user removed]

VX was lean burn with 16 valves. CX was 8 valves and no lean burn. The aerocivic had a CX engine in it until it was upgraded to a VX engine and appropriate wiring, ECU, etc.

You can see the difference in Basjoos garage logs.

regards
Mech

[outerspacio]

I have a 7-seater 2001 Corolla Spacio (JDM import - sold from 2002-3 as the Corolla Verso in Europe) with 1.5 1nz-fe and 4-speed auto. The engine is currently a non-runner and might cost more to repair than buying a replacement. I'm very interested to know if 1NZ-FXE has the same engine mounts. It's fairly likely I'd needed to customise a lot (driveshafts etc.) but the idea of a prius drivetrain in the more practical (if less aerodynamic) Verso bodyshell is very appealing as 90 % of my driving is flat motorway 70 mph stuff (don't need bags of power for that) and I'd be getting a significant lift in engine efficiency vs the 1nz-fe which is more standard running 10.5:1 compression. the inz-fe vvt-i provides intake cam advance but I don't think it has the same objective as the extended timing of the fxe, it's just to widen the torque band. Simpler than the whole drive train would just be the engine mated up to my existing transmission (U340E I think), but I don't know about getting the ECU you might reprogram for the 1nz-fxe to talk to one of those auto transmissions.... Guess I'll probably have to get another regular 1nz-fe :-(

[Cobb]

Mr Plug in Hybrid suggesting a Diesel?!?!?!?!

From what I can see this variant of the engine is used in a lot of Toys economy cars like the scions and such. Toyota NZ engine - Wikipedia, the free encyclopedia

Originally Posted by Daox

If you're wanting a higher efficiency engine, go with diesel. They beat even the atkinson engines in efficiency, and you have low rpm torque.