Should I turbo my M20?

[Hoffbrohaus]

I'm on the fence. I have an E46 M3 and supercharging will cost me over $8k. Looks like I can turbo the E30 for around $3.5k. It's a 1990 325is with 150k miles and it's in good shape. So I guess I'm just worried I'll blow the motor or somehow trash the car in some way. I had a 1998 200sx SE-R back in the day I turbo'd and it was a blast :)

[MrBurgundy]

It going to cost more than that to build something that will take a beating reliably. That may have been the budget for a decent build back in 2008.


You'd probably get it around 3.5k with ebay parts and a stock motor.

[reelizmpro]

Yes. It used to cost prohibitive back in the day but now you can get kits that are plug and play, even down to the engine management. The stock compression is 8.8:1 so it's low enough stock and with MLS you can lower it even more depending on how much boost you plan on running. So no need to change pistons or even do anything to the bottom end as there are people running 16PSI+ on stock internals except for studs and maybe O ring block for higher boost applications. If you plan on just boosting the stock engine, I hear they are good upto 16PSI or so. I'd say it's the most cost effective way to get real power from the M20 without modding the heck out of engine itself.

[varg]

Yeah it's generally cheaper than $8k. Cost is 100% dependent on goal., dpends on what you buy, it adds up fast and I'd say $4000 is pretty much the minimum for a decent setup. IMO this is the bare minimum: you spend $500 putting together a megasquirt kit, $700 header (it's on sale for like $550 right now), $400 injectors, $800 turbo, $100 VR44 wastegate, $500 clutch, $150 intercooler, $200 wideband, $100 fuel pump, and $800 on tubing, BOV, mufflers to weld up your own piping and exhaust. Little add ons like the turbo oil feed and drain, refreshed fuel lines, a boost gauge, will add a couple hundred more. Homebrew your way to turbo goodness with a fairly cheap setup very similar to mine. I've done it the super cheap way, old used turbos, ebay clutches - don't bother. My piping and stuff was dirt cheap ebay and junkyard takeoffs, I welded up an aluminized exhaust with a harbor freight welder for $300 in parts 7ish years ago. Upgrading for easier or better stuff like a MS PNP or a nicer wastegate or better intercooler drives the cost up. You can buy a $4,000 kamotors kit but completely omits exhaust and the intercooler is worse than my ebay 24x12x3.

there are people running 16PSI+ on stock internals except for studs and maybe O ring block for higher boost applications. If you plan on just boosting the stock engine, I hear they are good upto 16PSI or so. I'd say it's the most cost effective way to get real power from the M20 without modding the heck out of engine itself.

Meh, PSI of boost is basically meaningless without other context, you can run as many psi as you want with a small turbo, it doesn't mean you're going to make a lot of power. If you're going to talk about the limits of the stock engine, it's the power and torque guys have made with it reliably that matters. I've run 20psi on an unopened M20 with only head studs, I daily drove this turbo car for years at 17psi of boost. The turbo is not small, a 60 trim T04E with a 57mm exducer turbine, good for maybe 475hp if you had a big turbine housing on it. My setup falls off up top with the .63AR turbine housing, but it's pretty responsive and I get full boost around 3,500rpm, 4,000rpm in lower gears. If you put an S366 like what's going in my wagon on this thing and tried to run 20psi, you'd be in a different situation (boom). I don't beat on my car and it's tuned like a daily (no dyno queen "moon tune").

[82eye]

. It's a 1990 325is with 150k miles and it's in good shape. So I guess I'm just worried I'll blow the motor or somehow trash the car in some way.

you will trash the value of the car for sure. e30's are now old enough to be considered a modern classic. once modded they lose value. do it for fun if that is what you want, but understand you'll never recover the value of the car if it's in good shape now.

[AWDBOB]

If you're creative and don't mind having a little fun planning the project, there are plenty of ways to turbo your e30 on the relative cheap with decent reliability. The cast log manifold from e28goodies is awesome, Pulsar turbos are a great bang for your buck, and ebay intercoolers and piping have come a long way. There are plenty of reliable options for wastegate and blowoff valves that are cost efficient. 300hp in an e30 is an absolute riot.

[Hoffbrohaus]

you will trash the value of the car for sure. e30's are now old enough to be considered a modern classic. once modded they lose value. do it for fun if that is what you want, but understand you'll never recover the value of the car if it's in good shape now.

This was my concern. I feel like my car has a good pedigree and is a collector car at this point.

https://www.r3vlimited.com/board/forum/general-forums/general-discussion/336900-rcwells-325is

It's in great shape still, crack free dash, manual 2 door, rust free original paint etc. I'm thinking I better leave it be and either find a beater for $4k to turbo or just SC the M3.

[PEZ2]

Not having any M20 turbo experience I have a question for those who do. I seen over the years lots of turbo additions to unopened stock motors and have yet to see an explanation of the ring gap conflict. Seeing that NA engines ring gap on an M20 84mm bore is about 12 to 20 thousands, and turbo ring gap charts would indicate a much larger gap than the top of the range. So how do these motors run without end gap closure and premature engine failure?

[Panici]

This was my concern. I feel like my car has a good pedigree and is a collector car at this point.
It's in great shape still, crack free dash, manual 2 door, rust free original paint etc. I'm thinking I better leave it be and either find a beater for $4k to turbo or just SC the M3.

Any modifications you do from stock will reduce the value (although I'd argue an Auto to Manual swap is an exception to that rule).


Are you keeping the car long-term as a collector's item? Driving it for a few years and then selling? Plan to keep it long term?
How you answer will determine your path for the E30.


Personally I build my cars for my own enjoyment. I'll never get the money (or time) spent out of them if I were to sell, but it's not about that for me.
There are worse things to sink money into. At least at the end of the day I'll have some fun rides and good memories.

[AWDBOB]

you will trash the value of the car for sure.

This was my concern. I feel like my car has a good pedigree and is a collector car at this point.
https://www.r3vlimited.com/board/for...-rcwells-325is

It's in great shape still, crack free dash, manual 2 door, rust free original paint etc. I'm thinking I better leave it be and either find a beater for $4k to turbo or just SC the M3.

"trash the value of the car" is certainly a bit dramatic. A properly executed turbo kit on a 325iS just makes it more of a drivers car. Unless it has low miles, someone is buying it to drive it. Saying it'll trash the value I just really don't see as the truth. Well done 24v swapped cars bring all of the money. A well done turbo setup is no different. A collector just bought a super nice rust free '90 325iS from me to drive. It wasn't even remotely close to the caliber of the other cars in his collection, in his mind. A humbling perspective.

IMO, I had the collector car mentality on my last car, and it took all of the joy out of owning it. Are you a legit collector? If the answer is no, life is short, enjoy the car how you want to. Also, it should also be said that everything required to turbo an E30 is reversible. Keep all the stuff you pull off, problem solved.

Many of us have cars now that are "worth 20K", and it can sneak in and disrupt the enjoyment one gets from the car. A well maintained, properly driven car doesn't go down in value if you enjoy it and keep up with it, only a low mileage collector example does, but it's easy to let the idea that our cars are worth more than we paid for them dilute the enjoyment we get from these things.

Insure it properly, don't paint all of the fenders different colors and slide it into a wall, enjoy it how you want, and you'll be alright.

TURBO. Oh, and make a build thread when you do.

[Hoffbrohaus]

"trash the value of the car" is certainly a bit dramatic. A properly executed turbo kit on a 325iS just makes it more of a drivers car. Unless it has low miles, someone is buying it to drive it. Saying it'll trash the value I just really don't see as the truth. Well done 24v swapped cars bring all of the money. A well done turbo setup is no different. A collector just bought a super nice rust free '90 325iS from me to drive. It wasn't even remotely close to the caliber of the other cars in his collection, in his mind. A humbling perspective.

IMO, I had the collector car mentality on my last car, and it took all of the joy out of owning it. Are you a legit collector? If the answer is no, life is short, enjoy the car how you want to. Also, it should also be said that everything required to turbo an E30 is reversible. Keep all the stuff you pull off, problem solved.

Many of us have cars now that are "worth 20K", and it can sneak in and disrupt the enjoyment one gets from the car. A well maintained, properly driven car doesn't go down in value if you enjoy it and keep up with it, only a low mileage collector example does, but it's easy to let the idea that our cars are worth more than we paid for them dilute the enjoyment we get from these things.

Insure it properly, don't paint all of the fenders different colors and slide it into a wall, enjoy it how you want, and you'll be alright.

TURBO. Oh, and make a build thread when you do.

Damn it this is exactly what I'm saying, on the fence with the angel on my shoulder saying "don't do it, leave it alone it's perfect the way it is." and the Devil on my other shoulder saying, "DO IT! You love boost!!"

and you are right a good build won't trash the value, I loved this one on BAT https://bringatrailer.com/listing/1990-bmw-325i-63/

I don't have the cash to do one like that but I would do better than a budget build and still pay less than supercharging the M3.

[82eye]

"trash the value of the car" is certainly a bit dramatic. A properly executed turbo kit on a 325iS just makes it more of a drivers car. Unless it has low miles, someone is buying it to drive it. Saying it'll trash the value I just really don't see as the truth. Well done 24v swapped cars bring all of the money. A well done turbo setup is no different. A collector just bought a super nice rust free '90 325iS from me to drive. It wasn't even remotely close to the caliber of the other cars in his collection, in his mind. A humbling perspective.

IMO, I had the collector car mentality on my last car, and it took all of the joy out of owning it. Are you a legit collector? If the answer is no, life is short, enjoy the car how you want to. Also, it should also be said that everything required to turbo an E30 is reversible. Keep all the stuff you pull off, problem solved.

Many of us have cars now that are "worth 20K", and it can sneak in and disrupt the enjoyment one gets from the car. A well maintained, properly driven car doesn't go down in value if you enjoy it and keep up with it, only a low mileage collector example does, but it's easy to let the idea that our cars are worth more than we paid for them dilute the enjoyment we get from these things.

Insure it properly, don't paint all of the fenders different colors and slide it into a wall, enjoy it how you want, and you'll be alright.

TURBO. Oh, and make a build thread when you do.

an untouched car in the garage is definitely no fun. if you're keeping the thing long term a turbo is better than a clogged up parking spot. i agree with you over the market value of the car getting in the way of actually enjoying it. mine is not an is and it needs some work. because of that i would have no trouble modifying it. it's got 100kmi which is on the lower end of mileage for a non vert here.

clean is in slightly better shape would be a hard call. you don't see them here anymore. i've seen one is in the past year, a couple verts, and about five rusty e's. e30's are near unicorn status here.

[82eye]

Personally I build my cars for my own enjoyment. I'll never get the money (or time) spent out of them if I were to sell, but it's not about that for me.
There are worse things to sink money into. At least at the end of the day I'll have some fun rides and good memories.

this. do this.

my car will never be collector level. it was never going to get there when i got it either. doesn't mean it can't be really nice and have some fun at the same time. e30's can cover a lot of bases outside of collector.

[varg]

Value? A well executed turbo install is completely reversible. It’s not like you’re hacking up the sheet metal to fit an oversized engine in it.

Not having any M20 turbo experience I have a question for those who do. I seen over the years lots of turbo additions to unopened stock motors and have yet to see an explanation of the ring gap conflict. Seeing that NA engines ring gap on an M20 84mm bore is about 12 to 20 thousands, and turbo ring gap charts would indicate a much larger gap than the top of the range. So how do these motors run without end gap closure and premature engine failure?

I don’t know what the factory ring gap specs were but a majority of turbo M20 builds are old engines, the ring gaps aren’t what they were from the factory anymore with all of the ring and (sometimes) bore wear.

[ForcedFirebird]

Seeing that NA engines ring gap on an M20 84mm bore is about 12 to 20 thousands, and turbo ring gap charts would indicate a much larger gap than the top of the range. So how do these motors run without end gap closure and premature engine failure?

Where did you get .012-.020"?

Turbo applications .0055-.006 x bore diameter (3.307") = .018-.019". Almost EVERY ring set I have installed came out of the box at .018". I often don't even have to gap the rings, just check them (speaking of using OE Mahle replacement pistons in an m20).