B18B build up

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Originally posted by Blanco@Jun 18 2004, 05:55 PM
Right on. I thought I remember seeing something about a year ago about using 15% as the typical loss through the drivetrain (parasidic loss?). Originally I was going to go ITR, then I switched to GSR, then between an LS and a GSR and I think I might still rather have the GSR. Then I think that I just want the GSR for t3h Vt3CHzes and the higher reving abilty. And I do want to build this engine. Maybe I'll just build my A6 or a Z6 before dropping it into the DX hatch. It's a good thing I'm planning on waiting until after summer before doing anything with this motor. Bah I say, bah unto my indecision.

Just double checking. I'll be alright under 300whp, right? I really don't want to resleeve if I don't have to.

if you spend money to build a d-series, IMO, you're wasting yoru time and more so you're money.

boost the fuck out of it, and when it blows, buy another block for under $100.

you can blow 15 motors before you will get your money back ona sleeve/piston/rod job.

hell, im TRYING to sell an UN-blown z6 shorty with tranny for $50, and I CAN'T!!!!

under 300 whp, tuned properly, good fuel, good timing, you'll be relativly safe at a lelve below 300 whp.

if yoy're running an fmu, i'd drop that number to 200.
 
yeah< I am with pissed off!

I LOVE boosted single cams!

They make so much torque and are pretty reliable.

Jeff
 
lol 15%, you know that most vtec heads are close to 90% stock right? :|

The idea is that with more air, more fuel, and a more complete burn it will result in more low end power, and a quicker spool time.


Yah I know how that works, thanks :) I was saying maybe a 15% increase in VE. Obviously its not going to go over 100%.

Have any proof, formulas, or real world examples. Or just your guess? :p


I usually don't bother busting out math and finding examples. But as I remember it, 1 point of compression is usually good for 10whp. And while that 10hp is real great out of boost, at the same time your losing the relative ease of tuning + reliability you have with just using boost. That 10whp can easily be made up for by and extra pound or 2 of boost. I would post the numerous dyno charts of cars running sub 10, and even sub 9, compression and post perfectly good HP #s and track times. Who the hell races out of boost anyways? Especially on a B series transmission, your not even dropping out of VTEC when you shift, never mind dropping boost. Most any turbo your going to use on a street honda is going to be spooled by 4k no matter what. D series transmissions don't even drop below 4k from a redline shift.

If anything, I'd want to be sucking in as little fuel as possible under 4k to keep gas mileage in hand. I just don't see the advantage to using higher compression on the boosted car. It just plain isn't neccessary.


Its funny you change your tune now, originally saying that exhaust gas isn't increased as compression increases. Would you say that exhaust DOESN'T increase as hp does? :p


It prompted me to read a bit more on the subject, and yes, I decided I wasn't completely right. Considering the physics at first, it doesn't seem apparent that squishing something more has anything to do with adding more air. I didn't think much about the vaccum.

Its proven time and time again that you can safely run moderate compression, and it is better for performance. Period. Sometimes you have to realize there is always more to learn.


You can also run individual throttle bodies on an n/a car, and it's better for performance. It can also be done safely. It doesn't mean everyone wants the extra problems. It also doesn't mean that there aren't downsides.

You do realize that lots of aftermarket manufactures sell higher compression pistons than stock for stock turboed cars right?


Lots more sell boost controllers :)
 
I understand where you are coming from, I just see it as blown out of proportion.

There really is no rule, X amount of CR = X amount of HP

just like there is no rule that X amount of boost = X amount of HP

The idea being that you keep the same effective compression, just use more compression to get there. The performance gains are more than just top end, like increasing the boost (this of cource depends on the turbo and how long it takes to fully spool the extra 1-2psi)

Yes in all out race situations you are in the top end, but you still have to wait for the turbo to spool after the shift even if you do land at 4k. So an increase in spool time would be benifical. (unless of cource you are doing full throttle shifting or have some sort of misfiring system). On a road cource there are times where you have to manipulate the throttle. Better transient response can be crucial.

10:1 isn't a whole lot of compression. There are plenty of turbo gsr's that run that much CR daily, and plenty of ITRs that run that much on higher compression.

I don't see any reason to lower compression from stock. I wouldn't go to 11:1 unless it was a JRSC application, but 10:1 is very reasonable.
 
I think boosted single cams are great - I'll have one soon in addition to the boosted LS.
I will disagree with pissedoffsol on the built single cam turbo issue.
Using aftermarket rods and forged pistons is kinda retarded, but there are a couple of budget alternatives that make sense to me.
LS rods are the same length as D16 rods. Same size crank journal, 19mm rod journal (vs 17mm on most Ds.) and slightly thicker. Minor machining to thin down the rod so it bolts to the crank and voila you have a dirt cheap/free rod that is easily available that is good for 250-300WHP without any fear. Add in the Suzuki vitara G16A/G16B pistons with 75mm bore and you have a great combination for udner $150 for a Z6/Y8. For ZCs use the 98-01 GX piston that has the 19mm wrist pin and voila...

D series builds with bling-spec shit are retarded. If you're gonna stay D, stick with the budget mentality and (possibly?) get a little more creative about how you build the motor.

That is purely an opinion. Take it for what it's worth.
 
just out of curiousity, no one is claiming that any internal combustion engine is 90% efficient are they? because that's ludacris. and i dont mean the guy from the music.
 
Originally posted by radnulb@Jun 21 2004, 04:58 PM
I will disagree with pissedoffsol on the built single cam turbo issue.
Using aftermarket rods and forged pistons is kinda retarded, but there are a couple of budget alternatives that make sense to me.

oh indeed... even the panda setup is fine.

but to spend a G on sleeves, 500 on rods, and 400 on pistons on a d-block, to me, is retarded.
 
Originally posted by nismogod@Jun 21 2004, 04:29 PM
just out of curiousity, no one is claiming that any internal combustion engine is 90% efficient are they? because that's ludacris. and i dont mean the guy from the music.

volumetric efficiency and the efficiency of an entire combustion motor are two completely different things.
 
Interesting read. How does a higher compression piston by itself create more vacuum? It seems that the amount of vacuum created by a high cr piston versus a low cr piston would be trivial at best...Most of the VE gained by NA motors is gained at high lift points in the valve's cycle. I would have explained the whole "off boost" power gains as merely a result in higher effective compression off-boost. The more cylinder pressure the cylce has to start with, the more power is going to be produced, because the overall pressure in the cylinder will be higher. I've heard the high cr/low boost vs. low cr/high boost argument before. Neither is better than the other, it just depends on what you are looking for as far as how you want your motor to behave. High CR/Low Boost motors would seem to have a more linear response than a low cr/high boost motors. You wouldn't see as much of a surge in power; that would appeal to me, because I like the idea of linear power curves, and being able to predict how my car is going to react when I mash the throttle. I honestly don't want to just smoke the tires all day, and that seems to be the case with most low cr/high boost motors: they are kind of just off or on, not really any in between. I don't have experience driving a high boost motor, but reading about others' experiences with burning thru 1st and 2nd gear, I don't think I would like that kind of power delivery. But what can I say, I'm not really into turbos; NA is more fascinating; and the technology of turbocharging has pretty much reached its zenith as far as I have seen; NA is where all the technology is at. Just look at all the new motors that companies have been building these last few years for both bikes and cars.
 
Originally posted by nismogod@Jun 21 2004, 04:29 PM
just out of curiousity, no one is claiming that any internal combustion engine is 90% efficient are they? because that's ludacris. and i dont mean the guy from the music.

no, the volumetric efficiency of a vtec head is claimed to be 90%. It doesn't mean 90% engine (fuel -> power) efficiency, we all know that is wrong.

what that 90% means is that 90% of the possible maximum air/fuel mixture at 1 atm gets into the cylinder
 
Originally posted by MikeBergy@Jun 22 2004, 01:58 AM
and the technology of turbocharging has pretty much reached its zenith as far as I have seen; NA is where all the technology is at.

negative. There are experimental turbo designs on the table in R&D facilities all over the place. I can't remember how they work off the top of my head, I read about it a while ago. But there is no chance that the technology is maxed out.
 
How does a higher compression piston by itself create more vacuum? It seems that the amount of vacuum created by a high cr piston versus a low cr piston would be trivial at best


If you understand how vaccum works, it makes a lot of sense.

The area above the piston grows at a larger rate with the higher compression piston. This creates a larger pressure drop, and the atomospheric area outside of the valves is pushed in to try and equalize the pressure. But because there it is a lower pressure zone (than the low cr pistons) it travels in at a faster rate. This equals to better cylinder filling.

This is simmilar to how ITBs work so well. When the ITBS are wide open, and the air is traveling to try and equalize the low pressure created by the piston returning to BDC. At some point the intake valve is going to close so the air still traveling will bounce OFF the closed intake valve and create a low pressure zone. Much like the cylinder itself, air will travel into that zone at a faster rate to try and equalize the pressure.

At the right RPMs (depending on the length and diameter of the ITBS) the intake valve will open again as the air is trying to equalize and enter and overfill the cylinder at the faster rate.
 
Originally posted by StyleTEG@Jun 22 2004, 09:06 AM

If you understand how vaccum works, it makes a lot of sense.

The area above the piston grows at a larger rate with the higher compression piston. This creates a larger pressure drop, and the atomospheric area outside of the valves is pushed in to try and equalize the pressure. But because there it is a lower pressure zone (than the low cr pistons) it travels in at a faster rate. This equals to better cylinder filling.

This is simmilar to how ITBs work so well. When the ITBS are wide open, and the air is traveling to try and equalize the low pressure created by the piston returning to BDC. At some point the intake valve is going to close so the air still traveling will bounce OFF the closed intake valve and create a low pressure zone. Much like the cylinder itself, air will travel into that zone at a faster rate to try and equalize the pressure.

At the right RPMs (depending on the length and diameter of the ITBS) the intake valve will open again as the air is trying to equalize and enter and overfill the cylinder at the faster rate.

I get all of the above except for the part in bold. I don't see how the higher cr piston is going to effect a more rapibidly growing area above the piston, given the same bore and engine rpms. I am not saying that you are wrong, just saying that you sound like you are basing your argument on the wrong premises. If you are saying that by having a larger piston dome, the volume above the piston in the chamber increases at a faster rate than that by a low cr piston, I completely understand, and it is just a mix-up of units. But I don't think that miniscule amount of suction increase at low valve lift is going to make a big difference. Combined with a good flowing intake manifold and ports, I could see this being a more appropiate place to look for off boost power, but by itself would not do a whole lot. Most volumetric effiency gains are made at high valve lift situations, and by the time the valves are close to fully open, the vacuum difference between a high and low cr piston would be a moot point.
 
Yes volume, not area sorry.

But I don't think that miniscule amount of suction increase at low valve lift is going to make a big difference.

....

Most volumetric effiency gains are made at high valve lift situations, and by the time the valves are close to fully open, the vacuum difference between a high and low cr piston would be a moot point.


Sounds like a whole lot of guessing to me.

Before throwing away potential benifits of a different setup, maybe you should try and find some hard evidence that its not worth considering.
 
Originally posted by StyleTEG@Jun 23 2004, 12:54 PM
Sounds like a whole lot of guessing to me.

Before throwing away potential benifits of a different setup, maybe you should try and find some hard evidence that its not worth considering.

Well it actually wasn't my my thoughts, I must confess, the topic was addressed on m24x.com, and the guy for RLZ? I think was saying that. I am in no way in a position to do testing like that, and for the most part, it really is just a situation where you have to test two different pistons on the dyno, and see where the differences lie. It would be a guess for me, but like I said, I am just relating information I have seen posted by someone else with lots more building experience with me. Keep in mind that most of the VE problems come up with NA setups, not turbos, and most people building boosted motors are looking for the quick bang for the buck, not dumping a gagillion dollars into a race ready, highly responsive on-and-off boost motor. So basically I am in agreement with radnulb, recomending a lower CR and easing up the tuner's task of getting it dialed in. Tuning and dyno cost money, and the less time that is needed to get it all dialed in, that is more money you could be saving to put back into other areas of your car. But I see what you are saying, and I would prolly spend the extra cash to do a high compression build, because, like I said before, I am an NA guy, and a linear engine response is going be a lot more likely with the setup you were talking about.
 
Yes, Rocket has discussed this subject before. And it isn't easy to measure. However I don't think it should be dissmissed as "minimal" if no one has any real evidence one way or another.

I still have to disagree with some of your logic though.

While yes, most guys are looking for quick up and go when it comes to boost... you are already talking about rebuilding the engine in this situation. (What CR to go with, when picking new pistons).

So that isn't going to save you any money.

And as far as tuning, that is the last place I would want to try and speed up and get dialed in. As far as running boost is concerned, I would rather he spent an extra hour or two making sure everything is set.

The money you don't spend replacing your engine is money that can be spent elsewhere ;)
 
neglect the .7:1 compression difference and add yourself some nitrous. lol. sorry, not a valid point in this conversation. i like linear power curves. mmm. lol. i'm glad to see that people on this site have wonderful linguistic skills along with physics knowledge. i think i need to go back and finish my degree. perhaps i can make a difference somewhere

as far as tech being maxed out in any field, especially mechanics, i dont think its possible, atleast, not within any amount of time i will ever be alive.
 
Originally posted by Blanco+Jun 24 2004, 03:55 PM-->
@Jun 23 2004, 04:00 PM
Yes, Rocket has discussed this subject before. And it isn't easy to measure. However I don't think it should be dissmissed as "minimal" if no one has any real evidence one way or another.

I still have to disagree with some of your logic though.

While yes, most guys are looking for quick up and go when it comes to boost... you are already talking about rebuilding the engine in this situation. (What CR to go with, when picking new pistons).

So that isn't going to save you any money.

And as far as tuning, that is the last place I would want to try and speed up and get dialed in. As far as running boost is concerned, I would rather he spent an extra hour or two making sure everything is set.

The money you don't spend replacing your engine is money that can be spent elsewhere ;)

While I'm following this quite closely, I have to say this. I'm not about to spend $1000-1500 on dyno time for 1 point in compression, for a negligible pre/off-boost difference. If you can show me dyno charts of the same engine, running both 9.3:1 and 10:1 pistons, that shows both long-term reliablity and why I should worry about a .7:1 difference, I'll consider it. I don't have enough money to think outside the box when it comes to my engine build, I'm going with what's been tested and proven.

I want the temperature outside to be 74 degrees every day of the year, but its not, lets discuss why its hotter some days and colder other days. Thats what discussing why different compressions create different vacuums is to me. Why discuss something you can't change? if you buy X pistons, they create X vacuum. End of story.

Also, on some of the higher compression motors, if you stick your hand over the T/B or ITB it will suck it so hard, it will HURT your hand.

I datalog all of what your talking about all the time, thousands of times. I will go ahead and record some video's of high vs low compression on anf off throttle for comparisons.

Thats all you have to do, real easy. I just see 0 point to it. You can't change it.

74 degrees would be nice huh? Golf....

Jeff
 
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