Turbo Tercel

[SirFoxx]

Hey-

Just wanted to get everyone's (except petros..already know what it is and most can assume what it is if you've read enough of his posts ) thoughts and opinions on turbo'ing a tercel.

Do you think it'd be worth it if it could be done cheaply?

How much power do you think the motor can handle?

How much horsepower would you like to see out of a 3a if you were to turbo one?

How long do you think the engine would last?

Would you do draw thru or blow thru?

Stock carb or weber?

Custom manifolds?

Headgasket longevity?

[drafting3d]

deleted...

[SirFoxx]

The cooling passages in the 3A were modified in the 4A, which helped with headgasket issues.

Everyone says this but I have yet to see any tangible evidence of it being true. Do you have any links where people have opened up the heads and examined the water jackets?

A factory stock 3a with a 'J-pipe' exhaust manifold and a blow through weber would run, make great noises, lots of tuning to overcome. BUT....
its effort and work that could be spent on something else.
I still toy with the idea of rebuilding a 7afe block & balanced rotating assembly and then putting a 4AC head & big cam on, the combination would probably handle boost.

why blow thru vs going draw thru? Draw thru is arguably easier to do, assuming you either have or have converted a turbo to carbon seals to deal with the engine sucking oil in past the seals.

As someone who's done a 7a block with a 3a head, its not worth it. There is no corrective lower timing gear for the sohc timing belt, so you would have to get a 4ac adjustable timing gear and waste all of its potential correcting for the additional block height.

The transmission, would struggle to cope with the extra torque though.
Ive been inspired by other toyota 4K turbo projects (basic, pushrod, forklift engine) It would be cool to see a 4A do similar, just delicately to avoid head gasket problems.
You can get custom made gaskets, in single layer metal, with a specified thickness to alter compression ratio too.

Why do you say it would struggle? Turbo's dont only increase just torque, and there have been several people of have swapped 4age's into the wagons with ZERO transmission issues. The most power we've seen is from larry's 20v BT swap.

I may or may not already have a MLS HG on order...

As for power, depending on what maths used, I would say 135hp at the wheels, for a very short time. (100kw, which is what a basic cammed 4AGE makes, for 20 years reliably)

Why a short time? If you take the time and effort to avoid detonation with timing control and/or methanol injection, and keep the engine cool, it should last a good long time.

To get to 135fwhp, you'd need over 15psi. Thats what has me concerned. Unless you were able to improve the horsepower in NA form, then getting to 4age power will be a struggle.

Cheaply? Yes if you can weld and tinker and tune.
Then a big solid no, due to gearbox fragility, or is that grenadebox frag-ility?

Id much rather have a Bike carb setup for the fun of it, not worry about rising rate fuel pressure regs and all that jazz...

God I wish we could damp out the whole transmission fragility flame...yes, they can blow up if you are reaallllly dumb with them. But, we have yet to see one let go from sheer power alone.

You dont need to worry about rising rate fuel pressure if you do draw through since the carb wont be under pressure...

[Petros]

God I wish we could damp out the whole transmission fragility flame...yes, they can blow up if you are reaallllly dumb with them. But, we have yet to see one let go from sheer power alone.

we can not really address a pure power failure of the trans because these cars never came with much power. but there have been people on this forum that have had the fifth gear disintegrate when towing a small trailer, and we have also seen on this forum someone who had the gear cluster explode when backing up, and with the car still rolling backwards, put it in gear and accelerate forward. both of these conditions over loaded the gear box. there were also several forum members who had the front diff input shaft (trans output) shear off from off road use, and more than a few had the main input shaft get corn cobbed. There have also been several examples of failed front cv axles, including the spine shaft getting sheared off inside the front diff housing. some of this is likely due to low gear oil not getting lubrication up the front drivetrain, but it still hints at a gear box that can not handle a lot more power.

it would be difficult to find examples of T4wd trans that have been damaged by over powering it, since there are not that many examples of high engine output T4wds. getting much more power out of the 3a/4a engine takes a lot of effort, or a swap up to the 4age. examples of those are few and far between as it is. the 3a engine is not particularly reliable as it came from the factory, it does not have a reputation as good as the other Toyota engines, and there was never a large aftermarket demand for performance parts for the 3a, unlike the Honda, Mazda, and early Nissan counterparts. so there was never a good bolt on engine up grade package available to give the trans a good work out.

but I am with you on the trans not being as weak as their history suggests. I think with a good condition trans, or a recent rebuilt one up to factory specs, ran with a good mix of synthetic gear oil, and perhaps with some moly additive, it should hold up fairly well for up to perhaps 110hp at the flywheel, perhaps more. if the driver is always careful with the clutching and shifting, to apply power smoothly (as one should anyway), and not abuse it with adolescent "speed shifting" or towing too much, should make it hold up a long time. it seems to me one could also add an external oil cooler and perhaps a filter to keep the gear oil clean and cool. I have heard there are aftermarket trans filer/cooler kits that include an electric oil pump that can be adapted to the tercel gear box, but I would not think that would be necessary unless you will be racing it or using it in hot climates in a very aggressive way off road.

the rear axle should handle it, since it was originally designed as the main drive axle for the slightly larger RWD corolla, I have not heard of a lot of problems with the rear diff hat can not be traced back to neglected maintenance (leaky seal ignored). Too bad there is no easy LSD conversion for this size diff, it should take the extra loads on the Tercel4wd fine.

I think too, you are coming to these cars without a lot of long term experience with the Tercel4wd. Some of us on this forum have had many decades driving the T4wd, several had owned them from new (and have now passed away and can not contribute any more). I have owned and worked on over 20 Tercel4wd, about half had serious transmission issues. I have not had that kind of problem with any other cars I have owned or worked on. That is over 50 years of working on cars: the first car I bought was in 1974, and have since had experience with many Japanese brands, European cars, and a number of US made cars and trucks, in addition to other Toyota models. Sure, if people actually changed the gear oil in the trans, and had them checked for leaks like they should, it may not have been as bad, but this is a common condition with all used cars. I owned a '87 nissan pathfinder I drove 375,000 miles and neglected to ever change the oil, and sold it with the original clutch still in it working good. I my wife drove a Mazda MPV 4x4 van about 250,000 miles, auto trans, and we also neglected to change the ATF when we should have, yet it lasted longer than most Tercel4wd transmissions. it is easy to forget when it runs fine, and you always have other pressing issues to deal with. I do not know what else you need for proof, detailed study and break down of all causes of Tercel4wd transmission failures? you will never find that. cars develop a reputation usually with a good reason. the trans on the Tercel4wd is fragile, but workable with care. how much power you can push through it without it bundling up is a question most of us who have been on this forum for decades do not want find out. The cost and consequence is very high.

ignore the collective experience of those on this forum as you wish, you may be pleasantly surprised. or we might be saying "told you so" in only a few weeks. good luck.

[SirFoxx]

ignore the collective experience of those on this forum as you wish, you may be pleasantly surprised. or we might be saying "told you so" in only a few weeks. good luck.

I have no idea what you're referring to by ingoring the collective experience...Most of the failures you mentioned are caused by dumb people not checking the trans oil level. Plus, who tows with a unibody tercel? Seeing as they never came from the factory with a tow option, that would imply its not meant to tow stuff.

I too have thought about adding an oil cooler, one that pulls from the side of the trans, and returns it to the top of the input gear. Though, finding a pump that can easily pump thick gear oil will be difficult.

We already know the trans can take the power of a 20v BT 4age--155hp. Anything there and inbetween will be fine as long as you aren't dropping the clutch at every light. A turbo will never get a 3a to that power level unless you were to increase the VE of the motor (how well it breathes).

I'm surprised you haven't put two + two together--i am the guy on the fb page with the turbo tercel wagon. I mainly made this post to spur a conversation between the members that are not on the facebook page. I mainly did this build to see what happens, and guess what? The engine and trans are holding together just fine. The block will need to get bored again soon though due to it ingesting a metric crap ton of dirt from the meet n greet, as well as an oversite with a factory sandwich plate (it pulls oil from the unfiltered side of the oil filter).

[The Professor]

If it's cheap to build, easily forgotten when it breaks, and you don't rely on it to get around, then I say go for it. Sounds fun.

That said, I'm old enough to know that it is much more reliable/tunable to simply swap in a more powerful powertrain. There are reasons why fuel injection and turbochargers developed along a mostly parallel path...

Also old enough to not want to throw money at a project. Do it once, do it right (which to me sounds like the 20V engine, or similar).

But again, sounds like a fun, low-buck, low-risk project, so why not?

[SirFoxx]

If it's cheap to build, easily forgotten when it breaks, and you don't rely on it to get around, then I say go for it. Sounds fun.

That said, I'm old enough to know that it is much more reliable/tunable to simply swap in a more powerful powertrain. There are reasons why fuel injection and turbochargers developed along a mostly parallel path...

Also old enough to not want to throw money at a project. Do it once, do it right (which to me sounds like the 20V engine, or similar).

But again, sounds like a fun, low-buck, low-risk project, so why not?

Easily forgotten...ha, id have to look at it every day in the driveway if that happens.

As someone thats done a 7age swap into a tercel, I agree there are better powerplants that can be dropped in. However, hearing a turbo go choo choooo as youre screaming down the interstate is so much more pleasing.

I currently only have 500-700 invested (meth injection and turbo seal conversion + rebuild were the $$$ costs). The engine is holding together fine with 8psi being shoved into it. Wideband AFR helps immensely when tuning, getting the timing locked and meth injection have allowed to the engine to stay happy. End goal is 4age power, which should be doable with 15psi, or making the engine breath better.

I'll post pics here for those who arent on the facebook page.

[drafting3d]

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[SirFoxx]

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I take it youre wanting to see the pics?

[terceldude]

Hey-

Just wanted to get everyone's (except petros..already know what it is and most can assume what it is if you've read enough of his posts ) thoughts and opinions on turbo'ing a tercel.

Do you think it'd be worth it if it could be done cheaply?

How much power do you think the motor can handle?

How much horsepower would you like to see out of a 3a if you were to turbo one?

How long do you think the engine would last?

Would you do draw thru or blow thru?

Stock carb or weber?

Custom manifolds?

Headgasket longevity?

1. Yes
2. Almost unlimited if you cryotreated the gearing and heat vulnerable parts
3. At least 90 like the 3A-SU engine or 100 like the 4A-ELU. Maybe more if the mechanic was willing to give it as much umph as he/she can
4. If all heat vulnerable parts and tranny gearing were cryotreated, almost forever
5. don't know the Pros and Cons of either but possibly blow thru because the turbo has to force air in the engine not draw air from it
6. Dual Mikunis if poss.
7. Nope. Some already made for sidedraft carbs for said engine
8. Depends on brand you use

[Petros]

[
I'm surprised you haven't put two + two together--i am the guy on the fb page with the turbo tercel wagon.....

... The block will need to get bored again soon though due to it ingesting a metric crap ton of dirt from the meet n greet, as well as an oversite with a factory sandwich plate (it pulls oil from the unfiltered side of the oil filter).

I know exactly who you were from the first post. you just seem to think that all the trans failures are due to neglect. I have been on this form for well over a decade, have read nearly every post, and have driven and worked on T4wd for longer than that, as well as many other older cars. there are some cars that have manual transmissions that are nearly impossible to wreck, that is not true with the Tercel trans. And I did point out that if the trans is treated well, it should hold up fine. my own trans in my daily driver has some 400k miles on it, half of that with a lightly built up 4ac driving steep gravel roads daily. I can tell you, having worked on engines for over 50 years (starting with small engines when I was 11), it is a bad assumption to think you know more than everyone else when it comes to tweaking engines for more power.

Are you running an air filter on your intake? I discovered that will wear out an engine in a hurry, even when not driving dusty roads. Also, in a dusty environment the oil should be changed much more frequently, I found that out on my 4ac I had recently pulled with less than 100k miles on the rebuild. I was surprised to see the main and rod bearings well worn despite always keep the oil topped up, and doing regular changes. the gravel roads I drive must have also accelerated the bearing wear, and certainly contributed to cylinder and ring wear as well, I had to go next oversize piston and rings with the current rebuild. I will have to go to a 3000 mile oil change interval to keep the engine from getting worn out because of the area we live. I hate to put so much oil changes into it, but that is easier than a complete overhaul every 4 or 5 years. Normally 5000 mile oil change interval should hold up fine, but not if your car is exposed to dusty roads like mine.

[drafting3d]

After seeing this, its the perfect description of 'ghetto-fab'
https://www.youtube.com/watch?v=CG7i-QooBOM

[SirFoxx]

[
I'm surprised you haven't put two + two together--i am the guy on the fb page with the turbo tercel wagon.....

... The block will need to get bored again soon though due to it ingesting a metric crap ton of dirt from the meet n greet, as well as an oversite with a factory sandwich plate (it pulls oil from the unfiltered side of the oil filter).

I know exactly who you were from the first post. you just seem to think that all the trans failures are due to neglect. I have been on this form for well over a decade, have read nearly every post, and have driven and worked on T4wd for longer than that, as well as many other older cars. there are some cars that have manual transmissions that are nearly impossible to wreck, that is not true with the Tercel trans. And I did point out that if the trans is treated well, it should hold up fine. my own trans in my daily driver has some 400k miles on it, half of that with a lightly built up 4ac driving steep gravel roads daily. I can tell you, having worked on engines for over 50 years (starting with small engines when I was 11), it is a bad assumption to think you know more than everyone else when it comes to tweaking engines for more power.

Are you running an air filter on your intake? I discovered that will wear out an engine in a hurry, even when not driving dusty roads. Also, in a dusty environment the oil should be changed much more frequently, I found that out on my 4ac I had recently pulled with less than 100k miles on the rebuild. I was surprised to see the main and rod bearings well worn despite always keep the oil topped up, and doing regular changes. the gravel roads I drive must have also accelerated the bearing wear, and certainly contributed to cylinder and ring wear as well, I had to go next oversize piston and rings with the current rebuild. I will have to go to a 3000 mile oil change interval to keep the engine from getting worn out because of the area we live. I hate to put so much oil changes into it, but that is easier than a complete overhaul every 4 or 5 years. Normally 5000 mile oil change interval should hold up fine, but not if your car is exposed to dusty roads like mine.

Yes, I am running an air filter. However, I do need to replace it as half of the filter element are missing. It will likely get a rebuild as even before I did the turbo, when I had the head off all cross hatching was gone. This was a semi-fresh rebuild with sub 5000miles on it. Oh well.

I never said I know more than you peter. However, I do know more than you when it comes to turbo. When was the last time you installed one on a 3a? The only advice you give when someone wants to tweak these engines is "3A bAd". If someone wants to do it, then let them. It'll either end in happiness or disappointment. I've already accepted the fact that I may blow my engine up, especially since I am using a first gen 3a, which has smaller connecting rods than a 2nd gen 3a.

I also never said that the transmissions are impossible to wreck. All I said was we've never seen one go from sheer power. The rumor that constantly gets circulated about anything above 100hp will blow it up is really annoying as its not true whatsoever. Hell, I raced with a member here on the forum and he would rev his 4age swapped wagon to the moon and dump the clutch while it was in EL. Never a problem.

[SirFoxx]

After seeing this, its the perfect description of 'ghetto-fab'
https://www.youtube.com/watch?v=CG7i-QooBOM

Eh I would say thats fairly subjective. Ghetto would be using pvc piping and the turbo sticking 5 feet above the engine.

This video is out of date already. All the charge tubing has been replaced so I don't have the collapsing elbows. A removeable brace has also been made for the exhaust piping. None of the welds have failed, which honestly surprises me with the amount of weight hanging off the exhaust pipe.

I am not a fabricator or welder, nor do I have the tools to do proper bends and what not. The fact that it works and works well is an impressive feat in of itself. I am already running 8psi with methanol injection and my timing locked. I just purchased a 15psi spring for the wastegate. This may blow the bottom end out if I'm not careful. However, it should get me to 4age power levels.

[Petros]

I never said I know more than you peter. However, I do know more than you when it comes to turbo. When was the last time you installed one on a 3a? The only advice you give when someone wants to tweak these engines is "3A bAd". If someone wants to do it, then let them. It'll either end in happiness or disappointment. I've already accepted the fact that I may blow my engine up, especially since I am using a first gen 3a, which has smaller connecting rods than a 2nd gen 3a.

Hey look, no problem, I am not telling not to do it. I am not stopping you. please do not take my comments as being critical., more power to you. Good for you for giving it a try. Seriously. it will be interesting to see your results. I am just sharing some experience so you may be able to benefit from it, so you can perhaps take some precautions to counter what may become troublesome. And I doubt the early lighter connecting rods will be a problem, toyota tends to way over kill the low end (compare the 3a rods to say a similar size honda civic engine, which has more power output). I would not worry about the crank or connecting rods, it is the head that will be the limiting factor I think.

while true I have never put a turbo on a 3ac, I do have some turbocharging design experience. And perhaps you do have more turbo experience than me, I only worked for AirReasrch turbo charger division as an application engineer in 1981-2. we designed turbo systems for production cars in the early 1980's (when I worked there) for all the US, Japanese and European cars that used an AiReaseach turbo system, I designed the systems, the EFI, induction, specified the size of the turbine and compressor (A/r ratio) to optimize performance, and over saw the dyno testing, and mapped the performance, of the preproduction prototype engines. I also published technical articles on the performance of turbo changed engines in academic journals. During that time I also worked for the racing division of Nissan when they ran a factory backed turbo charged 300ZX race car (I assists with the engine development, induction, cooling system and the suspension) from 1978-84 (on and off for different projects). the 300zx race car used a production based 3.0 liter engine that was tweaked with the turbo to put out over 900 hp. that car was undefeated when it was running the IMSA circuit.

what is the extent of turbo charging experience do you have?