4AGE: 20-v Head Swap?

[rayfast]

This may be a dumb question, but can/should a 20-v head be installed on a 16-v 4AGE?

I have 1986 MR2 4AGE NA project car and I need to replace a blown head gasket. I was going to have the head checked and, if necessary, reworked while I've got it off. I have no interest in doing a complete engine swap, but I was wondering if a 20-v head can be bolted onto my block and what other mods would be required to pull it off. Is this a good or bad idea and why?

Thanks in advance for your feedback,
Ray

[mr220v]

It can be done, but from a cost and time standpoint, there's no advantage.

A problem you'll have is the different pistons. I believe the 16v pistons will clear, but the motor will no longer be noninterference. Also, compression might be down around 9:1. You could replace the pistons while the head was off.

The other problem is the number of parts you'll need from the 20v. You would basically need to go out and buy a motor anyway. This might work if you have access to somebody's blown 20v, say it spun a rod bearing and you can get the whole thing for $50, but generally going out an piecing a 20v together is going to cost more than buying a working motor.

So, in almost all circumstances, it's cheaper, easier, and more reliable just to go get a 20v and swap it. Going the head swap route, I think you'd ultimately end up doing 110% more work.

[scottohno]

so this is an unplug, drop out, drop in, plug in kind of experience?

[toyotaspeed90]

Originally Posted by scottohno

so this is an unplug, drop out, drop in, plug in kind of experience?

not even close....

to run a 20V head you need to use all of the 20V components... the ITB's, the wiring, injectors, distributor, ecu, etc.....

there is a way around all of this, but I haven't been able to completely find the last piece of this story (getting a 20V to work on a 16V ecu)... also, I don't have anything to try it out on anymore, as my friend got rid of his 20V long ago....


Actually... I'm going to edit this.... I know 100% how to get a JDM 16V map setup to work on a 20V engine and keep the whole thing plug and play.... but I don't know how to make what I need for the US setup.... there's 1 component that's specifically different between the two where I can't find that different component on a US motor that already exists.... nor is it easy to recreate.... if I figure it out... I will probably sell it as a kit.

[mr220v]

^Yeah, the distributor on most usdm cars is different vs the smallport or the 20v.

It could certainly be done....but will run like who knows what. There would be the distributor to buy, and you would have to run smaller injectors as you will now be running batch vs sequential. The 16v harness is not compatible with the 20v, so extensive rewiring will still be required.

Getting a 20v ecu just isn't that hard or expensive.

[toyotaspeed90]

Originally Posted by mr220v

^Yeah, the distributor on most usdm cars is different vs the smallport or the 20v.

It could certainly be done....but will run like who knows what. There would be the distributor to buy, and you would have to run smaller injectors as you will now be running batch vs sequential. The 16v harness is not compatible with the 20v, so extensive rewiring will still be required.

Getting a 20v ecu just isn't that hard or expensive.

wiring the internals of a 4afe distributor to a 20V ecu would be cake.... in fact, we did a 16V 4age (JDM) dizzy on my ae92 (which uses a 4afe ecu)... there were some wires that had to move (similar in an AW) but the wiring would be very straight forward and simple.

I have yet to find the components to make the correct dizzy that works on the USDM 16V ecu....

I wouldn't be concerned about the injector size.... they are larger on the 20V... however, the compression (and probably quantity of air coming in) is higher on the 20V than the 16V.... it's not a direct correlated percentage, but will get it pretty darn close. My 4afe (smallport injectors) is a good example -- it didn't pass emissions but still gets over 30mpg at 60mph (and higher, the faster I go).

[mr220v]

I haven't found a 4/1 multiwheel trigger to run the 20v....I guess you could mod the 20v distributor to do it.

You would have to do something about the injectors. The 20v injectors are 113cc's larger. Not quite twice the capacity, and actually larger than the DLI GZE injectors

[toyotaspeed90]

From what I have always read.... the 20V injectors are 290's.... a bit larger than the smallports.... all gze injectors are 365's.....

I have the correct housing and the correct shaft.... but I went through 6 different brand bits trying to get the pin off either dizzy (using my drill press) and couldn't get it out.... that was a few years ago when I attempted that one....

[mr220v]

I was looking at the late smallport size on that. Smallports are 235's.

The chart I was just looking at had the bigport at 182cc, and the 20v at 295cc. You do have some flexibility, plus or minus 25% on newer ecu's, but I think we're outside of what the bigport ecu will compensate for on this one. Hard to say for absolutely sure though without trying it.

On the other hand, I was able to slap a 1zz ecu on my beams car, and it actually managed to cruise pretty well. I don't know what the injector difference was, but the 1zz runs at a higher fuel pressure.

I think you'd want to snag some smaller sidefeed injectors.

The jdm smallport ecu could probably run the 20v as-is. The bigport would be more of a problem. I guess if we have to spend money on ecu's we may as well spring for the correct 20v ecu. They are pretty cheap.

[toyotaspeed90]

Smallports should be 250's..... 4afe's are 178 or somethin, and IIRC bigports are 210's....

Which chart are you using?

What they are rated at is determined at what fuel pressure they were tested at.... I've seen some people claim their bigport (blue) injectors running over 260.... but then you look and it's at like 45psi....

[mr220v]

It's the chart in the club4ag tech reference section. It has been up for a decade or so, so I would imagine it's accurate as it has yet to be corrected:

Club4AG - Tuned Toyota Automobile Enthusiasts

Fuel pressure has a lot of bearing on fuel being delivered. The only general change of pressure I'm aware of was when they went to returnless type systems. It seems like the return type regulators are all running the same pressures since we're able to use 4/7afe regulators with the 20v with no issue.

[mr220v]

Also, that's not to say that the motor wouldn't run with excess fuel, it just wouldn't run all that well. There are a number of other factors that might make a 16v ecu'ed 20v run not so well. Even what looks like the most compatible of the 16v ecu's, the jdm smallport, is probably not the greatest.

It's an academic argument. From a cost/effort standpoint, there's no advantage to running a 16v ecu of any kind on a 20v (except maybe to satisfy curiosity). I pick 20v ecu's up for $50 sometimes.

[toyotaspeed90]

well, yes and no....

20v's are becoming the new GZE (in price and availability), so this idea is relatively moot.

However, it's easily viable to go to a junkyard (if you can find the dizzy)... pick up the dizzy, and a handful of pigtails.... buy some wiring and some butt connectors.... extend a few things (like the dizzy wiring) using the pigtails, and you have a 100% unmodified harness that if something were to go wrong with the 20V, a 16V could be put in within a day (or less) with no more wiring other than unplugging your extension cables.

however, your comments sound exactly like what the ae86 guys said when they first saw my ae92 on a 4afe ecu.... that was ~6 years ago and in terms of the ECU it runs great... in fact it dyno'd pretty darn well for the condition of the engine too.

either way, no big deal... I know it can be done and would expect it to dyno within probably 5% of a 20V on a 20v ecu... bore, stroke, adjustment factors are essentially the same... everything will get scaled up on a 20V if you use the 20V injectors then modify the 16V ecu


and just for some fun poking.... I had heard you sold a 20V to someone over here (in WA)... one that was in your car running.... well, after a couple weeks of them unsuccessfully being able to get it started it was me (who is anti 20v) who got it started in a sea of 20V guys (this is meant to be taken very lightly, fyi)

[mr220v]

^Yeah, I remember that. From what I heard, it turned out to be nothing but a set of wires and a cap. The thing is that the 20v tune up parts are hard to get, so people avoid replacing them like the plague. They tried everything but that.

Nobody ever said you don't know your ****. Getting that swap running sure helped Donny out, not to mention the buyer of the motor.

Don't get me wrong, I'm by no means against using a factory ecu from one motor on another. I have another project I'm working on which should be pretty slick when it's done. I'm not going to mention anything about it right now, but it could probably catch on.

Since you mention the 4afe ecu, I would think a 94 or so 4afe ecu would be the ideal alternative to running a 20v. Just a few dollars in the junkyard, it's known to work with the 20v, still might have a less than desirable sized set of injectors, but different injectors would only be a few more dollars anyway.

If you swapped in a 96-97 7afe oilpump crankgear and pickup, you could even look into running 1zz powerfc's. That could probably work too with a 4tooth crank pickup.

With a bit of research, and time to mess with it, a lot of this stuff could turn out really useful. That's the problem, time is limited. If I followed up on all these cool little things that are out there, I'd have to quit my real job.

[mr220v]

Originally Posted by toyotaspeed90

(who is anti 20v) )

Why be anti 20v? It's a cheap alternative to building a 16v motor up with a bunch of aftermarket parts, and is competitive with the stock usdm GZE. I'm not big on the GZE (or the 3sgte, or certain v6's, etc....), but I wouldn't say I'm "anti" any of these motors. I've wired for all of them,

At the end of the day, these are all relatively low powered motors...at least compared to what we built this summer.