turbo or 24v swap?

[Hooffenstein HD]

M52B28 is the way to go. That aluminium block.

[nando]

Not in the USA.

[digger]

Say you have M20s, both make 200whp. One is turbocharged, one is NA. Both engines are experiencing the same internal stresses, one has a compressor forcing air in and the other has head work and a cam letting more air in. The turbocharger isn't going to miraculously wear out the engine 2x faster because it's there, and the turbo itself can go on and on for 100,000mi or more if you stay on your oil changes and don't do stupid stuff like shut the engine off immediately after beating on it or expose the turbo to surge conditions. Turbochargers are not unreliable. If you satisfy the cooling demands of the engine, it isn't miraculously going to blow up faster than the NA one because there's a turbo hanging off of it. You're judging all turbocharged systems based on shoestring budget and hacked together trash you see on forums - stuff like my car. And even then there are exceptions and reversals to the common anecdotes of turbocharged engines blowing up. While I've beat on my low budget turbo M42 endlessly over the past year, it's still driveable, this summer I saw 2 bone stock M20s die catastrophic deaths. If you take care of it, don't tune it poorly, and cool it well, a turbo engine will last. Especially an understressed one like a 250whp M20. Turbocharger bearings are an additional wear part, sure, but they last a long time if you take care of them, same as the bearings on your crank and rods.

this is not always correct, the turbo engine can and often will make more peak torque and torque through the mid range for the same peak hp number (depending on specs etc). Thus the cylinder pressures and inlet temperatures involved would be higher in that case, so more likely for tune issues and such . obviously both can be safely done but its in no way the same

[varg]

this is not always correct, the turbo engine can and often will make more peak torque and torque through the mid range for the same peak hp number (depending on specs etc). Thus the cylinder pressures and inlet temperatures involved would be higher in that case, so more likely for tune issues and such . obviously both can be safely done but its in no way the same

Well if you're bent violating the assumption of equivalent power output that I used for that hypothetical exercise sure. You can shape the torque output of a turbocharged engine by varying boost or using different configurations, of course, and that changes the peak cylinder pressures and where they happen, but in the end you control peak cylinder pressure and the rates at which it changes, and keep it in the "let's not bend any rods today" range with a good tune which I already mentioned. You can make the hypothetical 200whp turbo M20 with a very small turbo so that it makes full boost just off idle and has a flat torque curve or use one that is sized so that the power builds linearly like it does with the NA engine. You still aren't going to significantly effect the longevity of the engine either way, we aren't talking about shooting for giant record setting power here. All discussions of longevity and reliability are pointless once you start talking about ambitious power figures. You're going to run into longevity concerns either way once you start trying to make crazy power, NA or turbo. The torque monster 600hp 2.5L turbo engine might have these insanely high peak cylinder pressures at peak torque to lift the head and whatnot and the 600hp 2.5L NA engine is going to be revving to an obscenely high RPM figure which doesn't exactly go hand in hand with stuff lasting a while and not needing a rebuild every season.

The, what, 150f peak post IC inlet temperature? Has no effect on engine longevity so I'm not getting the point of mentioning that.

In the end, the "turbocharged engines are just less reliable" thing is a tired trope that really isn't relevant anymore. Very high performance and reliability are fairly incompatible in any capacity, but for moderate performance you've got your turbo-consuming audis on one hand and your million-mile turbo diesels on the other. Turbocharged engines run the gamut, do it right and you have no immediate or long term concerns vs just building a high-power NA engine, besides the cost maybe.

[nando]

Meh. New factory turbo engines aren't much better. N54 anyone? Like i said, its fun while it works.

[ak-]

A turbocharger has two moving parts. A rotating assembly, and a wastegate. Turbochargers are not inherently unreliable. If you don't neglect them, they will last a long time. This is not 1975.

A bad tune or insufficient cooling will kill a built NA engine, that's not exclusive to turbo stuff, it's just easier to do. If you do it right, it will last!

It's not that simple.

Wastegate line comes off? Boost into oblivion = motor is toast with 1 WOT pull.
Wastegate diaphragm tear? Same condition, wastegate won't open.
Fuel pump decides to go weak? Severe lean condition = melt a cylinder with 1 WOT pull.
Dying injector? Same condition.
Is there a surge tank? Same condition can apply on a long sweeper if gas is low.
Do you like meth? Great, lets introduce another pump to the equation.
Car decides to burn a bit of more oil than usual? Prolonged gradient lean conditions = ruining your octane value/slowly destroying the motor every pull.
But wait! There's more! Though I won't keep listing, lol.

Everything is being stressed more on f/i applications. Your compression ratio is being raised significantly. N/A is static and a vacuum the way it was "supposed" to be. Yes, I do agree that you can build the motor to prevent faster wear, but ultimately there ARE more variables that ruin things in the blink of an eye rather than N/A, where it's more of a slap on the wrist.
And we're not even on the heat management of things yet.
Don't get me wrong though. I love turbo motors and my ideal track toy WOULD be the turbo charged M20 (it's the long term end-game for my car that's been turbo'd for 3+ years), but not for the factor of power and being different, but more because I would enjoy building it to perform against all the odds of pulling me backwards and I love tinkering.

For guys like OP going in head first with no base yet, I wouldn't advise a turbo m20 for the track. It'd be overwhelming trying to get everything right.

[2mAn]

M52B28 is the way to go. That aluminium block.

Not in the USA.

Its post like these that make me feel like a winner



...carry on...

[TobyB]

But boy, are they fast for the 3-4 laps that they work..

For guys like OP going in head first with no base yet, I wouldn't advise a turbo m20 for the track. It'd be overwhelming trying to get everything right.

This.

If you've instrumented well, have a fast, easy- to program ECU, good tuning,
first- rate components everywhere, you can get a track turbo car to hold together with
limited boost.

But wait- OP has never been to the track. So the last thing he's going to be
doing is watching oil pressure going through the esses...
...and when it hits full boost coming out of seven, how's the snap- oversteer on lift?

I recommend 24v, whatever way works for wherever you are, if you're really serious
about doing HDPEs.
But it's your call.
Whatever you think you'll be more likely to finish, that's what you should do.

t
(but if you put a turbo in it, you'll have a hard time getting an instructor
to hop in with you when you're in the novice group!)

[redsubdivisions]

Not true. Turbocharging doesn't make things less reliable if it's done right. This isn't 1975.


There's plenty of NA garbage that wouldn't last half as long as a low boost turbo M20.

Thank you! This kind of mentality drives me nuts.

[haaken675]

I think at this point it's going to come down to which one I am going to be able to make a/c work on...I want to be able to actually drive the car on the street and here in Florida a/c is a must have...

If I can make the turbo work with a/c, I think I am going to go that route as I can build it slowly.

[redsubdivisions]

I think at this point it's going to come down to which one I am going to be able to make a/c work on...I want to be able to actually drive the car on the street and here in Florida a/c is a must have...

If I can make the turbo work with a/c, I think I am going to go that route as I can build it slowly.

It can be done, particularly with a water to air setup so that way you have room for the aux fan to run at idle.

You have to pay to play in this game. Cars are not cheap hobbies.

[haaken675]

It can be done, particularly with a water to air setup so that way you have room for the aux fan to run at idle.

You have to pay to play in this game. Cars are not cheap hobbies.

I'm not too keen on water/air intercoolers. Everything I have read about them says they tend to heat soak, especially on track. And trust me, I completely understand the pay to play part...This e30 is my second e30, my 5th BMW, and my 9th car and 10th vehicle...That on top of my 3 motorcycles, two of which are hand built...I definitely understand the money part :D

[varg]

Wastegate line comes off? Boost into oblivion = motor is toast with 1 WOT pull.

Wastegate diaphragm tear? Same condition, wastegate won't open.

Are you serious right now? Any tune that is within a million miles of halfway decent has this little thing called overboost protection. Boost hits a preset point? It cuts fuel and spark. No damage. You set overboost protection to a safe level, and you can weld the wastegate shut and never damage the engine by overboosting, it'll just cut out as soon as the boost reaches the overboost threshold. Your sig says you have a turbo 325is, how on earth do you not know what overboost protection is? I am baffled.

Fuel pump decides to go weak? Severe lean condition = melt a cylinder with 1 WOT pull.
Dying injector? Same condition.
Is there a surge tank? Same condition can apply on a long sweeper if gas is low.

This all applies to NA engines as well! Do you think lean conditions damaging an engine are exclusive to turbo engines? I'm not even going to bother going further since you are implying only turbo engines blow up when they go lean at wide open throttle. If your NA engine isn't an understressed lump of tractor parts like an M20 or M10 is bone stock, it's going to damage something if it goes from 13:1 to 16:1 while you're thundering down the back straight of your favorite track at wide open throttle approaching the rev limiter. It sounds to me like you're comparing understressed stock engines to 400hp turbocharged monster M20s, it's just not a smart comparison.

[nando]

nah. It really won't. You'll (noticeably) lose some power, but it's not going to explode. Also, the likeliness of that actually happening on an N/A motor is far lower.

[varg]

nah. It really won't. You'll (noticeably) lose some power, but it's not going to explode. Also, the likeliness of that actually happening on an N/A motor is far lower.

Any engine making a high specific output is at risk if it goes lean. You can't just go comparing an understressed 170hp lump which can run lean all day to a high strung turbo engine and tell people turbos are bad because you'll blow the turbo engine up if it goes lean. If you're going to compare you have to compare like things. Whether you're making 150hp/l turbo or NA, you're endangering your engine by going lean under load.