Supercharges vs. Engine size.

[RomanV]

In another thread, Fivebob made this interesting comment:

However IMO you're wasting your time using a supercharger on a 4A, turbos are a much better option. S/C's come into there own on bigger engines where the drive loss isn't so noticeable, but that discussion is another topic altogether.

Ive thought about this before, and I agree.
But I cant say that I know why, perhaps I am just judging this from 4agze to 4agte conversions.
Why is this the case?

I know that a V8 leaves a rather nice space for an SC between the banks, but surely there is more to it than that.

I suppose an asthmatic car with oodles of torque would benefit the most from an SC, as it can use some of the low end torque (that it has spare) to spin the SC, and it allows the engine to breath a bit better at high RPMs.

Whereas a highly strung engine, that is optimised for high RPMs....
Has cams, intake runners, exhaust manifolds, etc. etc. all tuned for high RPMs... which means it has little torque at low RPM. This, combined with trying to turn over an SC, means a big loss in low end torque. Despite the extra airflow to the engine. (Or does it? is the boost enough to compensate for it?)

What are your thoughts on the matter?
I know that there arent too many people here interested in superchargers. As turbos just seem like such a better option,
for most of the engines in toyotas that people choose to modify.

Is cost a big part of the equation?
I know that decent superchargers are rather pricey, compared to a similar turbo, which will invariably deliver more HP.

The 4agze is the only commonish 'small' supercharged engine that Ive ever heard of, except for a few kei class cars, which are supercharged or twincharged.
I dont doubt that there is a good reason for this.

[barryogen]

In another thread, Fivebob made this interesting comment:

However IMO you're wasting your time using a supercharger on a 4A, turbos are a much better option. S/C's come into there own on bigger engines where the drive loss isn't so noticeable, but that discussion is another topic altogether.

Ive thought about this before, and I agree.
But I cant say that I know why, perhaps I am just judging this from 4agze to 4agte conversions.
Why is this the case?

I know that a V8 leaves a rather nice space for an SC between the banks, but surely there is more to it than that.

I suppose an asthmatic car with oodles of torque would benefit the most from an SC, as it can use some of the low end torque (that it has spare) to spin the SC, and it allows the engine to breath a bit better at high RPMs.

Whereas a highly strung engine, that is optimised for high RPMs....
Has cams, intake runners, exhaust manifolds, etc. etc. all tuned for high RPMs... which means it has little torque at low RPM. This, combined with trying to turn over an SC, means a big loss in low end torque. Despite the extra airflow to the engine. (Or does it? is the boost enough to compensate for it?)

What are your thoughts on the matter?
I know that there arent too many people here interested in superchargers. As turbos just seem like such a better option,
for most of the engines in toyotas that people choose to modify.

Is cost a big part of the equation?
I know that decent superchargers are rather pricey, compared to a similar turbo, which will invariably deliver more HP.

The 4agze is the only commonish 'small' supercharged engine that Ive ever heard of, except for a few kei class cars, which are supercharged or twincharged.
I dont doubt that there is a good reason for this.

I'm not going to claim that I know all on this subject because clearly I dont.

But essencially, from all my research on turbo'ing or SC'ing my car(2zzge engine seems to be a replacement for 4age), I have found that there are two groups, those that want to make it a lot faster(the turbo boys), and those that want to make the powerband wider and more predictable(the SC boys).

Now having a small NA high rev'ing engine is nice, I do miss having a low end, the 2zz is dead below 4k RPM, now by dead I do not mean undrivable, I just mean torque wise, it is(or atleast feels) rather lacking, now to me, an SC seems like a better option, as it would give me the bottom end that I would like(to make it a bit better performance wise round town without having to rev it's tits off), but the scotsman in me wants a turbo as appears to be a slightly cheaper route.(also being a high comp NA engine full boost should be there at ~2500RPM anyway for the combination I'm looking at.).

Now, to address some of your comments.

The 4AGZE to 4AGTE conversions happen as the SC on the 4AGZE was pretty bloody small, and an "easy" and "cheap" upgrade is changing to a turbo, as bigger SCs cost more(probably due to economies of scale more than aanything.

Yes V8s have a nice gap for an SC, but that isn't really the reason... I mean why do Holden and Ford now do Turbo'd versions of their V6/8 cars.(not sure on whether it is both 6 and .

Having lotsa torque at low end is handy to spin a SC, but isn't really necessary as such... they give you more than they take away(physics aside).

If I'm wrong on any of this, someone correct me, but I think I covered most of it.

[Stealer Of Souls]

I don't really know any reasons. But I think that smaller (street driven) engines are more suited to SC than TC.
After all, you're looking for the big engine feel from a small engine, and you don't necessarily want there to be any obvious changes in power delivery if your just puddling around the streets or cruising down the country.
But I have to admit. The drive losses would have a greater effect on a smaller engine.

On a personal experience not.
AW11 SC with auto box is a great round town car. Plenty of low down go, and when you wind them up a bit the auto box (having long legs) really lets you fly along with little effort.

[Mr Revhead]

yeah after buying my s/c aw11 im a firm fan of the s/c.
the instant low down torque just cant be replicated by a turbo. well, not by one that wont strangle it at the top end.

if the set up is designed properly i dont see how size would be a factor.

also i think a s/c is easier to set up for most applications.
i dont mean the actual s/c setup but i mean the whole car as a package.
when a turbo falls off boost its a pig. so you need to play around with sizes and/or gearing to suit. s/c dont have that problem to the same degree.

but when it comes down to the application is what you need to think about.
if your after max hp for drag racing then turbo is probably the way.
if you need a good fat instant torque spread say for hillclimbs, then s/c is better imo

[Ako]

Also depends on the engine size that you're working with.

For little midget engines then sure, every little bit helps. A properly sized engine can get away with a lot more than a tiny one - just look at what driveability can be coaxed from a 2JZ for example with big power.

And I won't even start on rotaries - they just break all the rules for lag (or lack of it)

[Dell'Orto]

I dont know that torque would mean too much either for a small motor turning a supercharger, as the pulleys would help overcome this surely?

[willsf1]

I think that regardless of engine size a supercharger will drain a proportion of the crank power relative to the amount of air it is pumping. For example on top fuel dragsters the supercharger drains something like 600hp, ofcourse it more than compensates for this loss by the additional volume of air being burnt.

A turbo will for the same amount of boost add less heat to the charge than a roots or screw supercharger and drain no power from the crank. It does however use energy from the system by taking momentum out of the exhaust stream and creating back-pressure. Once crossover is reached though (where inlet man pressure exceeds exhaust man pressure) a turbo can really make power. Crossover isnt really possible on street engines but an 4agte setup running 8psi should make a good 50hp over an sc on the same boost due to no crank losses and better thermal efficientcy which is the key, its a heat engine afterall.

[Mr Revhead]

i would be suprised if an sc12/14 would heat the air more than the average turbo on a 4agte. certainly roots type create some heat, but as theres no exhasut there build up heat transfer they only have to contend with compression heat.

thermal efficiancy takes into account the exhaust gases which is wasted in a s/c setup so they always win there.

[Ako]

I'd hazard a guess that every single person who has gone to a turbo swap on their ex - SC 4age has found more power on the same boost. Okay, there will be an ever so slight delay while it comes on boost, otherwise driveability doesn't HAVE to suffer.

Also remember - there is a difference between LAG and BOOST THRESHOLD, which a lot of people don't realise. Lag is time taken from foot flat to feeling power, say at 5000rpm. Any well setup turbo should be almost instant in delivery once revs are up, if not, try coming into the 21st century

Boost Threshold is what people often mistakenly call "lag". Its the point where useful boost is being made - you can have a laggy, yet responsive turbo setup if you really want, and would probably be what I would call most decently powerful 1600 - 2L turbo engines. It also varies with load, so people will argue about it till the cows come home.

I think its one of those things you have to actually experience to understand fully, otherwise you'll be lead astray by what internet experts are telling you.

[Mr Revhead]

yes going from a stock 4agze setup to a turbo will gain HP. as its a custom setup and you can pick parts to match
however hp is not important, torque is
id much rather have masses of midrange and weak top end than weak low-midrange and mega top end. but thats because my goal is hillclimbs and twisty stuff in a midengine car.

again it comes back to use.... this is one of those questions where there is no firm 100% answer that suits everyone.

so as always, when chosing a set up, think about its purpose, $$ avail and ease of install/parts

[Ako]

Its only the most extreme turbo setups which give you just top end - try driving an evo and tell me its lacking um.. anywhere in the rev range.


Though like you say, horses for courses. I just love the big hit in the back you get from a 4500rpm spool up... brrrrrrrrAAAAGHRHRGHHG sums it up phonetically

[IH8TEC]

I'd hazard a guess that every single person who has gone to a turbo swap on their ex - SC 4age has found more power on the same boost. .

i got 101kw atw on 12psi with s/c
and 125kw atw on 10psi with turbo

my turbo has pretty useable power from 2500rpm, just gotta use your gears really compared to the supercharger.

[willsf1]

I got to used to the power of the sc in my aw sure driveability myt be an issue with a turbo setup.But to be honest although the sc coulb be on boost at 1500 rpm it didnt really do much until 4000 boost at low revs is just hard on a motor probably why 4agze pistons are semi-forged and 3sgte are not. I love the mid eng handling of an aw the turbo factor just makes the driving more chalenging, look at the turbo cars of the eighties sure their budgets where astronomical but its the principal that counts. Superchargers only exagerate the law of diminishing returns.

[IH8TEC]

probably why 4agze pistons are semi-forged and 3sgte are not.

dont start that one again, lol, go to the tech section and have a read


the thing with the supercharger to be honest, yeah you get instant boost, i had nearly 6psi at 2000rpm, but the car could not use it, it was stupid, now i ask you all, driving around town, how many of you drive round at say 1500rpm (be honest). when mine was s/c the initial boost build up was fast, but after that by the time it gets to full boost of 12psi by 4500, my turbo would beat it there as i get 18psi at 3500rpm

now with my turbo setup, i normally drive round town at say 2500rpm, and at that my turbo can have abotu 4psi if i put my foot down, and it goes, but my boost build so quickly from there it makes it more useful than the s/c.

each to their own though i guess,

[KE20]

my turbo on my 1jzgte doesnt hit 14psi untill about 5000. but once its hit it. whole sh?t it moves , but i want more down low.
what you guys think about putting say a eaton m45 on a 1jz, i know its big, and ive seen it used on lexus v8's, but i would flow heaps of air, so should have heaps of air down low and all the way to the rev limit. which should give a nice torque and power curve. and a bypass valve or similar would be needed so the boost level doesnt get stupidly high thru the rev range?

[gdsup]

I'd hazard a guess that every single person who has gone to a turbo swap on their ex - SC 4age has found more power on the same boost. .

i got 101kw atw on 12psi with s/c
and 125kw atw on 10psi with turbo

my turbo has pretty useable power from 2500rpm, just gotta use your gears really compared to the supercharger.

perhaps the other mods you did like intake manifold and intercooler during your conversion helped make that difference, as my s/c setup with improved intake and cooler made 122kw on 10psi, in saying this im sure any decent turbo setup on my application would make at least 10% more..

Edit : my point is the inlet and outlets of the sc12 are ghey factory, the throttle body is minature, and inlet manifold on 4agze is crap

[Si]

my turbo on my 1jzgte doesnt hit 14psi untill about 5000. but once its hit it. whole sh?t it moves , but i want more down low.
what you guys think about putting say a eaton m45 on a 1jz, i know its big, and ive seen it used on lexus v8's, but i would flow heaps of air, so should have heaps of air down low and all the way to the rev limit. which should give a nice torque and power curve. and a bypass valve or similar would be needed so the boost level doesnt get stupidly high thru the rev range

What turbo are you using exactly?

[barryogen]

now i ask you all, driving around town, how many of you drive round at say 1500rpm (be honest).

not 1500, but usually 1800-2400

I'm heading overseas(holiday) in a few months, and have organised a ride in a turbo, and an SC version of my car, basically I just want to see which suits my driving style, but I suspect it will be the SC.

Like IH8TEC said, each to their own, it is and always will be a personal preference, as a general rule, Turbo will make better in the mid to high end, and SC(depending on type) can do low to mid, low mid to high, or right through the rev range but more at the high end, again, it's personal preference.

[no_8wire]

now i ask you all, driving around town, how many of you drive round at say 1500rpm (be honest).

not 1500, but usually 1800-2400

3200 normally...mmh turbo teritory... Plus Revhead honestly when you are attacking the twistys do you no have the engine ringing out in the top of the rev range?...I on I do, but maybe thats because I dont have any FI...

[barryogen]

now i ask you all, driving around town, how many of you drive round at say 1500rpm (be honest).

not 1500, but usually 1800-2400

3200 normally...mmh turbo teritory... Plus Revhead honestly when you are attacking the twistys do you no have the engine ringing out in the top of the rev range?...I on I do, but maybe thats because I dont have any FI...

probably best to have it sitting at the rev line for greatest torque... mine is 6800, I'd imagine that the AW one is markedly lower.