What's important and what's not for making power...
9sec9 I feel like my car picked up power from bumping compression to 9:1 and adding 12mm of stroke and .5mm bigger pisotons..
You need to bump the compression of your sons car to 10:1
You need to bump the compression of your sons car to 10:1
Increasing compression ratio is, in theory, the best way to achieve more power, all other things remaining equal, because it provides substantially higher cylinder pressure, which translates to torque, which multiplied by RPM, equals horsepower.
Unfortunately, all other things do not remain equal, and you have to take into account the effect changing compression ratio has on the entire system. If just upping compression ratio to 10:1 (without corresponding changes in a number of other parts) were the simple solution, everyone who changed out their stock pistons would have been doing it...
My review of his posts suggests that 9sec9 has a pretty good idea of what he's doing already.
What 9sec9 pointed out when starting this thread was simple and straightforward. If you are planning modest increases in your HP over stock, building a complete bottom end is an unnecessary expense. Yes, there is the possibility that certain choices in a bottom end build can yield some (minor) HP increases. That is not the reason you build a bottom end, however, and the cost vs. increased HP, in isolation, would make that a pretty pricey way to pick up a few HP. If you plan to make big horsepower, building a complete bottom end (before you suffer a expensive failure) is a cost savings, as well as a stronger foundation for your other higher HP parts. You simply need to understand the difference in goals in order to make a good decision on whether a bottom end build is necessary for you.
Unfortunately, all other things do not remain equal, and you have to take into account the effect changing compression ratio has on the entire system. If just upping compression ratio to 10:1 (without corresponding changes in a number of other parts) were the simple solution, everyone who changed out their stock pistons would have been doing it...
My review of his posts suggests that 9sec9 has a pretty good idea of what he's doing already.
What 9sec9 pointed out when starting this thread was simple and straightforward. If you are planning modest increases in your HP over stock, building a complete bottom end is an unnecessary expense. Yes, there is the possibility that certain choices in a bottom end build can yield some (minor) HP increases. That is not the reason you build a bottom end, however, and the cost vs. increased HP, in isolation, would make that a pretty pricey way to pick up a few HP. If you plan to make big horsepower, building a complete bottom end (before you suffer a expensive failure) is a cost savings, as well as a stronger foundation for your other higher HP parts. You simply need to understand the difference in goals in order to make a good decision on whether a bottom end build is necessary for you.
Last edited by CO_VR4; Mar 27, 2008 at 08:58 AM.
this is also incorrect.
building a bottom end CAN make power. different piston dome shapes, ceramic piston coatings, different compression ratios, different stroke lengths, different cylinder bore, anti friction coatings, knife edged crank, lighter pistons, lighter rods, will add reduce parasitic losses/make for a more efficient burn/in effect make more power. if your going to the trouble to build a motor at least some of these steps will be taken, even if the gains are minimal.
building a bottom end CAN make power. different piston dome shapes, ceramic piston coatings, different compression ratios, different stroke lengths, different cylinder bore, anti friction coatings, knife edged crank, lighter pistons, lighter rods, will add reduce parasitic losses/make for a more efficient burn/in effect make more power. if your going to the trouble to build a motor at least some of these steps will be taken, even if the gains are minimal.
Scorke
Last edited by scorke; Feb 16, 2008 at 01:22 PM.
Example, someone on a budget that allows them to do a mod here and there, wants to go fast this summer.
He could save up all his $$ for a year or two or more, and do it all at once, and have a built motor and a fast car. Problem, he's been bitten by the speed bug and wants to go faster now....
So you don't have the money to go built motor yet, but you could go with a smaller turbo and supporting mods, right? sure... that's a nice waste of 1700 bucks if you already know it won't be fast enough in 6 months... speed bug again.
So what's happening is people are getting the big turbo kits, sacrificing some drive ability, and just buying what they need to get it to work... so later, when the funds are there to actually get internals, coil on plug, and other things.. they already have the big turbo waiting to turn up the boost and make more power.
It's all about horsepower to dollar. you get the car and put a TB exhaust on it... good gains... MBC, great! Cams, excellent... those things you can really feel the difference. Now the next time you've got a few grand to play with... what's the biggest bang for the buck.... well, I can give you a hint, it's not building the engine or sending your trans in to Shep.
It's difficult to do these cars one mod at a time, if you're the type that isn't sitting on a gold mine and really wants to feel an improvement every time they shell out another thousand bucks... it is a very difficult thing to spend the money to build an engine and drop it in to get.. pretty much no gain compared to the $$ it costs.
If there is a way to "get away" with something, guaranteed there will be someone there trying to do it. It doesn't mean it's a smart thing to do, but it will be done. And it might blow up. Might not though.
He could save up all his $$ for a year or two or more, and do it all at once, and have a built motor and a fast car. Problem, he's been bitten by the speed bug and wants to go faster now....
So you don't have the money to go built motor yet, but you could go with a smaller turbo and supporting mods, right? sure... that's a nice waste of 1700 bucks if you already know it won't be fast enough in 6 months... speed bug again.
So what's happening is people are getting the big turbo kits, sacrificing some drive ability, and just buying what they need to get it to work... so later, when the funds are there to actually get internals, coil on plug, and other things.. they already have the big turbo waiting to turn up the boost and make more power.
It's all about horsepower to dollar. you get the car and put a TB exhaust on it... good gains... MBC, great! Cams, excellent... those things you can really feel the difference. Now the next time you've got a few grand to play with... what's the biggest bang for the buck.... well, I can give you a hint, it's not building the engine or sending your trans in to Shep.
It's difficult to do these cars one mod at a time, if you're the type that isn't sitting on a gold mine and really wants to feel an improvement every time they shell out another thousand bucks... it is a very difficult thing to spend the money to build an engine and drop it in to get.. pretty much no gain compared to the $$ it costs.
If there is a way to "get away" with something, guaranteed there will be someone there trying to do it. It doesn't mean it's a smart thing to do, but it will be done. And it might blow up. Might not though.
Wow....I feel like you were talking directly to me for a second.
I fit this category 100% unfortunately.
BR Race fmic with pipes, HKS 280 cams, meth, fuel pump, turbo back, coilovers, suspension bars, a lot of weight savings, rims/wider tires, etc..............Stock viii turbo.....where to go from here? My goals are much bigger than an fpgreen so whats the point of buying one for now.
On the way:
BR HTA 35R
HKS DLI 2
780 injectors
So I don't have $$$ for a built tranny or bottom end right now. But my car is NOT my daily driver so with minimal miles per year and a good tune on stock ecu I hope I will be OK. I assume I will run 28psi on meth and hit right around 500whp on a dynojet.....for daily use driving. But how long will it hold up
I hope with good a/f ratios and meth tuning somewhat conservatively...........but I am well aware things could go wrong with this much power.
I've actually got our systems back up and running 100%.* Added 22 million records out of Texas that I didn't have before the crash, so I'm actually ahead of the game now.* Changed backup drives to a better/faster drive.* Life is good again.*
this makes me consider building my car before i bother with an upgraded kit at all...but there's no one in oklahoma that can build it and being deployed makes it a bit hard to take the car anywhere far..blah..
I agree with you 9sec9 on the reason for making this topic.
I'd like to give some input.
First, I've made 500+ whp on our dyno on stock engines quite a few times. Making that kind of power on the stock bottom end is no problem. Hoping it lives forever is another story......The biggest problem I feel is not the power as much as it is the RPM. When a car makes 500+ whp on our dyno it is going to cross the finish line in 4th gear at over 8,000 rpm. Running high RPM on the stock engine is what I feel is the number one reason for stock short block failure.
Weakest part in the shortblock? The rod bolts. Number two weakest, the piston.
The picture of the cracked piston in this thread is not an isolated issue, we've seen it on a few engines. I have also seen them completely seperate horizontally, so the top is left in the bore and the bottom is still attached to the wrist pin.
Is there power to be gained in the shortblock? Yes, of course. In the case of what 9sec9 is trying to convey the power gains are small. Both engines we have built for him (two different EVO's) the bore has stayed stock, the compression has stayed stock, stroke has stayed stock. The gains in this case would be from the elimination of the balance shafts.
I feel that if you are building a Stage 1-4 EVO then the stock shortblock is excellent. The car can run the 1/4 mile and not exceed what I feel is safe RPM levels (on most cars anyway). When the Green, race gas and an AEM EMS go into the equation the power goes up and the MPH goes up, this means the RPM is going up too. I've had stock shortblocks go 10's with the green and quite a few more run 11.0's. These cars ran for a very long time. One of them eventually had a rod bearing failure on a road course, the other broke a piston pulling away from a stop light. Both of these particular EVO's were very lucky and there was no real damage done with the failures.
My opinion is IF you DON'T have the money to do a rebuild if/when your engine blows up then you better find it now and do the build. If you have the money to gamble with then do what makes you feel best.
If you have a good block and you do not blow up your engine you are going to save yourself quite a bit of money. Here are some things you can very well expect to damage if you blow up your car:
Shortblock $1850
Oil cooler $350
Crankshaft $750
Cylinder head $1300
Valves $16 each
Now consider if you have a good core and nothing damaged you can do one of our Stage 3 shortblocks for $3,000. As you can see, the core fees to try and repair a blown engine are very high.
I'd like to give some input.
First, I've made 500+ whp on our dyno on stock engines quite a few times. Making that kind of power on the stock bottom end is no problem. Hoping it lives forever is another story......The biggest problem I feel is not the power as much as it is the RPM. When a car makes 500+ whp on our dyno it is going to cross the finish line in 4th gear at over 8,000 rpm. Running high RPM on the stock engine is what I feel is the number one reason for stock short block failure.
Weakest part in the shortblock? The rod bolts. Number two weakest, the piston.
The picture of the cracked piston in this thread is not an isolated issue, we've seen it on a few engines. I have also seen them completely seperate horizontally, so the top is left in the bore and the bottom is still attached to the wrist pin.
Is there power to be gained in the shortblock? Yes, of course. In the case of what 9sec9 is trying to convey the power gains are small. Both engines we have built for him (two different EVO's) the bore has stayed stock, the compression has stayed stock, stroke has stayed stock. The gains in this case would be from the elimination of the balance shafts.
I feel that if you are building a Stage 1-4 EVO then the stock shortblock is excellent. The car can run the 1/4 mile and not exceed what I feel is safe RPM levels (on most cars anyway). When the Green, race gas and an AEM EMS go into the equation the power goes up and the MPH goes up, this means the RPM is going up too. I've had stock shortblocks go 10's with the green and quite a few more run 11.0's. These cars ran for a very long time. One of them eventually had a rod bearing failure on a road course, the other broke a piston pulling away from a stop light. Both of these particular EVO's were very lucky and there was no real damage done with the failures.
My opinion is IF you DON'T have the money to do a rebuild if/when your engine blows up then you better find it now and do the build. If you have the money to gamble with then do what makes you feel best.
If you have a good block and you do not blow up your engine you are going to save yourself quite a bit of money. Here are some things you can very well expect to damage if you blow up your car:
Shortblock $1850
Oil cooler $350
Crankshaft $750
Cylinder head $1300
Valves $16 each
Now consider if you have a good core and nothing damaged you can do one of our Stage 3 shortblocks for $3,000. As you can see, the core fees to try and repair a blown engine are very high.
In my case I decided to build my bottom end and the top end long before it was strictly necessary for basically two reasons:
1.) Insurance - I road race the car, and I want my block to survive.
2.) Powerband - I knew that by upgrading the turbo I would effectively push the powerband of the car beyond its gearing. Given the stock gearing, my shift points with simple bolt-ons were already approaching 7600+ RPM. Now, with a 50 trim on the car, they're closer to 8500 RPM. What would be the point of making all that power if I can't use it to full advantage? In other words, on a road course I want to be able to rev out to my optimal shift point and on a 1/4 track you're going to want the xtra revs to keep it in 4th.
So far I think my decision was warranted, since the block has survived two bad valves (undiagnosed for 12 months, ugh), popping out a spark plug, and a few overboost situations.
l8r)
