lww

Uhhh... What? Some of the best 3.2 L Rebello & Sunbelt NA stroker's I've seen are below 270 wheel hp.

When your power band is up in the 4000 rpm range on that "flat powercurve" because of the cam you're using, my turbo that is making 15 psi at 2200 rpm is going to be smoking past it like white lightening. Oh, and I DO have baffles in my custom oil pan...

The only reason racers don't use forced induction is because the rules don't allow them. Where it is allowed, it is widely used and NA cars are far behind on the competative curve.

frank280zx

Than you have a small AR exhaust housing ... im all for that and run a .48 on my build.. but that is fairly agianst popular believe

I have seen 300 HP strokers to the wheels.. they do run more than 12:1 compression ( i think somewhere in the 14 region, but i can still drive 12 on pumpgas! )

jfairladyz

But what octane is pump gas in the netherlands? Cause I dont know if 91 octane and 12:1 c/r will mix too well

FubarI33t

Nismo, I am just gona use the head and block from a turbo setup. Since the F54 block is stronger then a non turbo. It would be better for a bore of such size.

NismoPick

Roger that big buddy. I was just wondering why you're not going turbo, if you already have everything to go turbo.

FubarI33t

I really just don't want the huge hassle of a turbo setup. boreing it out to a 3.1 stroker, geting work on head and intake. a mild cam. be all the power i need. I never have been a power hungry persion. Plus i am about to start restoring a old Fiat Spyder. Don't worry, it ain't for me, so no way is it gona replace my Z.

lww

You are correct and I do give up some top end power for the quick turbo spool & response. Although, I will be replacing it with a new turbo, hopefully this month which should put me at about 12 psi around 2500 to 2800 rpm, but give me more on the top end for minimal loss in spool time and since mine is a 3.1L stroker, I don't loose too much torque on the bottom end from the lower compression as a result of the greater displacement.

The key here is to engineer what you want, not just throw a bunch of parts together and then see what you have, like so many people do.

Unfortunately, 12:1 compression is mostly outside the realm of pump gas here in the states and definitely in CA, unless you have a Sunoco with 104 octane or a 76 with 108 octane at the pump.

Also, remember, the equation for calculating octane is different in the states than it is in EMEA/APAC. Their 98 octane is actually equivalent to our 93 octane as a result of differences in how the numbers are calculated.

I would be hesitant to run an NA 12:1 compression on 93/98 octane unless I had a high level of confidence in my fuel/spark management. Deficiencies in either will kill the motor post haste. Of course, at 25 psi my engine is generating the equivalent of about 20:1 compression in the cylinders... But I don't turn up the boost that high unless I'm running 108 octane... The boost controller usually sits between 12 & 15 psi which puts the calculated compression at between 14.5 and 16:1.

frank280zx

You did your homework.. most people dont know about the way octane is measured diffrently!! and yes i had confidense in MsS.. my rodbearings did not

To get back to the question i think a stroker or higher cr car makes more alround driveable car... that in the hands of most of us would even be faster (more easy) driven.

BTW are you at MSA ?

dreco

I'm very happy with my N/A stroker...but I think I'll go turbo next time around

SHADY280

i built my motor too "racey" when i did it, i had 12:1 on the street with the 1mm head gasket and i made it work with 94 octane, but it was hard. ive scine lowered it to 10.8:1, much more drivable, now if i only had ms. i think trying to squeeze all you can from a na is cool but there is no substitute for turbo power, my buddies na does 13.5 in the quarter, yet his poorly tuned moded turbo does 11.2, either way there both fun, and both zeds.

lww

No, I'm not at MSA...

frank280zx

why not im there and you should be there as this is your only change of meeting me for a while LOL

NismoPick

He's not an MSA employee (which is what your question sounded like)... but I think he's planning on being there. You gunna be there Frank? I still haven't ever figured out your story.... Are you still in the Netherlands, or the US? Cuz didn't you have some Z friends in Minnesota ?

frank280zx

Yeah Tyson is a buddy but im in The Netherlands... But then a gian Tony Digehare si a pal to... ooh well after MSA hopefully i have a llot more pals !

lww

I was just teasing you frank. I am currently planning on being at the MSA show this year. However, work is starting to cut considerably into my project schedule.

I have a trip to India scheduled from April 14th to April 23 which isn't going to leave much time for me to finish when I get back.

My ZXT may not be re-assembled in time, so I may have to take my 240z... if I can get the engine put back together and the new tranny installed...

Otherwise, it's Honda time! If I get stuck in the Honda, I won't be bringing the family, so I'll be mooching off the rest of you to crash in one of your hotel rooms...

FubarI33t

Well. The 3.1 stroker kit will have to wait a another week or so. I have a unexpected bill (Cough, Midget MG) pop up out of no where. so I'll let ya'll know when i am ready to get the block bored, i might need a lil help on the number's, Complicated number's and I do not get along very well.

NismoPick

keep this link handy:

http://www.ozdat.com/ozdatonline/enginedesign/

frank280zx

To set my point of High CR engine with a flat curve, i would like to qoute LWW in another post, about headers;


The distinction between "maximum power" and "maximum performance" is significant beyond conversational semantics. Realistically, one header may not produce both maximum power and maximum performance. For a vehicle to cover "X" distance as quickly as possible, it is not the highest peak power generated by the engine that is most critical. It is the highest average power generated across the distance that typically produces the quickest time. When comparing two horsepower curves on a dynamometer chart (assuming other factors remain constant), the curve containing the greatest average power is the one that will typically cover the distance in the least time and that curve may, or may not, contain the highest possible peak power.


Turbo cars tend to have ( the way most of you guys set them up, with big AR's on both sides low CR high boost numbers) maximum power, not the highest average power. High(er) CR strokers have mostly fairly flat curve compared to a turbo car ( depending on cam and whatnot) so would theoretically be faster

lww

Good one Frank!

Remember, for competition, you design an engine to produce maximum power over a specific rpm range, say 5000 to 8000 rpm. Then, depending on the track, you gear the tranny and differential to maximize the time spent in this rpm range, therefore maximizing your average power to realize maximum performance at that venue.

Of course, as I believe you intended to explain in your post, street cars have considerably different design criteria and operate in a much wider 'practical' rpm range. However, as long as someone can keep the motor in the rpm range that delivers the greatest average power production, it's my opinion that the low CR turbo will exceed the performance of an equivalently designed high CR NA motor with the addition of greater fuel economy when not applying that power in 'normal' driving.

I'm not sure of anyone else's build, but my motor looses about 2500 rpm on each shift and my car produces maximum torque at 4800 rpm and maximum horse power at 6700 rpm with a 7000 rpm (self-imposed, ignition limited) redline.

When I shift at 6950/7000 rpm, my rpm's drop to ~4500 rpm, close enough to my engine's greatest torque and near the top of my horse power curve, making it so I have the potential to produce really good average power.

jfairladyz

But your point is vague and really doesn't fall in line with what lww said. You're saying a high c/r will make a flat curve. Thats a little to general of a statement. Why would a 12:1 c/r motor have any flatter of a torque curve then a "turbo" car. A high compression ratio motor is just as limited in its power production as a turbo car. The name of the game is getting the cylinders filled. Well the wee little cam that will allow the high c/r to start it's torque curve early is going to limit it's maximum power, Severely. So what if the high c/r can start making power at 2k rpms. If it can only make so much horsepower after a given RPM then its average power output it going to be lower than a turbo motor that starts making it's power at oh, lets say 2500rpms and it just keeps making power all the way through the power band. Sure it loses 500rpms to the na but once that boost hits at 2500 it's all power all the time. And what you're forgetting is that a turbo motor only makes it's static c/r when it's off boost. Once it hits boost its making a lot more than it's static compression ratio. And if it's coming on boost at nearly the same RPM as the na starts making power than the whole power curve of the higher c/r engine is tossed right out the window. Especially when the turbo motor is the one that ends up with the higher c/r. Of course you could alway throw a bigger cam in the na. But then you'd start making power later and still wouldn't make as much power as the turbo. So the average is still going to be lower than that properly matched turbo.

The ONLY reason you see a peaky torque curve on a turbo motor is when someone decides to throw a HUGE turbo on their motor. A turbo that comes on boost at a low RPM is going to have a better torque curve than the na will. Turbochargers make Torque. I dont know why there is such miseducated assumption that they are "peaky". Anyone who thinks turbos are peaky are either trying to make insane power or dont know how to size a turbo.

jfairladyz

Damn, took me too long to type it

lww

This is the crux right here and to some extent supports frank's point. The VAST majority of people build their STREET motors to make maximum power to the exclusion of everything else. There are a few 'enlightened' builders out there that understand maximum average power over a specifically designed & engineered rpm range will produce a superior performing vehicle.

Real race teams understand this and know how to build for maximum performance within the engineering limitations of their cars.

jfairladyz

Yeahs thats what I was trying to say. It's that poor selection of components that leads people to believe they're peaky. But his statement was just so general in stating that a higher c/r will make more average power than a turbo. And thats just not true. Maybe more so then a improperly selected turbo. But not just a turbo in general. A turbo really is the ULTIMATE power adder, and if properly sized has no drawbacks other than cost of purchase. A turbo can make the low end power you want. Or you could size it to make your car a dyno queen. It really has no limits. An NA is very limited in how much and where in the power band it makes that power. People think NA and just assume it's going to make power from nil rpm all the way through the power band. It doesn't work that way. An NA is more limited in it's power band production than a forced induction motor is. An NA is almost entirely dependant on the size of it's cam. You can increase the flow before and after the cam all you want but if the cam doesn't let the air pass then it's all in vain. With forced induction it forces that air passed so you dont have to rely on the cam to do the work. It goes on and on but the bottom line is that a turbo can mold the power curve however you like and there is not beating the power of a turbo. Sure you could get a flatter torque curve from a 500HP 700ci na motor then you could from an L28ET. But then we'd be comparing apples to fruit alternative

SHADY280

j's last post there supports my car. its na, and you can feel the cam come in at about 3800 and go until 7200. i have all the air it can handle coming in, and msa headers going out 2.5 exhaust, so that leaves the flow part to the cam. on a turbo car, the turbo really determines flow in the engine. it is the most efficient power adder. and 2 small turbos will yeild better overall performance low and high because they can spool quicker at low rpm and put out at high rpm, plumbing just sucks though. after driving a both kinds of cars, turbos are neat, but at auto x, the large single turbo car doesnt have the snap the well built na does, it needed the time to spool and get into its operating range, auto x doesnt offer that room, and both cars had 3.9 gears and same trannys, and competitive tires. now on a drag strip or road race car this would be the opposite, the turbo can really shine. now im talking 280zx and this statement may not apply to other motors.

frank280zx

Well most people in teh US or better on these boards DO built them wrong ( i.e. stock internals and t3/4 with .60 ar exhauses ( i use a .43 so there is NO lag)

the stock compressiosn is very low.

In a turbo the powercurve will always be diffrent from a NA high CR or stroker for that matter ( given it has a mild cam fo street and 'sundayracer" track days ( even with a cam it would still be flatter)
as a turbo starts making power with boost !

to bad i dont have two sheets handy ... ooh well

What im saying is that when i read Hybrid, zcar and here i see sizes to make the car a dyno queen! (borrowed that expression)

Or mainly aimed at drags i think...
My .43 AR exhaust house will limit my PEAK hp, but will boost my avarange HP !


A turbo built right wil rock... but for street driving a CR engine would be my choice, as for amateure track driving