rod ratios/ longer rod
05-23-2006, 06:52 AM
#11
1.5 BAR
Join Date: Aug 2003
Posts: 1,164
Re: rod ratios/ longer rod
But that would require a custom crank which would be $$$. If your really worried about it run a gsr crank which is about 2 mm shorter stroke. Otherwise eagle does make the longer rods and someone does make pistons with the pin changed to the correct spot...i think its endyn but im not sure. But i dont think that its worth the money.
05-23-2006, 03:29 PM
#13
3.0 BAR
Join Date: Aug 2005
Posts: 1,654
Re: rod ratios/ longer rod
Originally Posted by boost_guy
With a 2mm longer rod you are talking about a .03% decrease in piston speed, and 2% decrease in maximum piston acceleration. That's less than the difference between the B18b and B18c. It's not worth it. 8500 rpm's is not going to be that big of a deal if you select the proper components and build the engine properly.
The only way to really make a dent in piston acceleration is to decrease stroke. Im not completely familiar with Honda B-series engines, but (theoretically) you could use a b20 block, destroke it to 1.8 liters, use a custom rod, and custom pistons. You could play around with the rod length and stroke a bit, but you would probably end up with a rod to stroke ratio around 1.7:1. Is all of that time and money spent worth it? Probably not. There are advantages like less wear on the cylinders, and increased dwell time at tdc(which has multiple advantages in itself), but in a street application they are negligible.
Trying new things is great, but it rarely turns out the way it's supposed to. Concentrate on getting the clearances perfect, getting your quench area right, balancing, and matching parts that work well together.
The only way to really make a dent in piston acceleration is to decrease stroke. Im not completely familiar with Honda B-series engines, but (theoretically) you could use a b20 block, destroke it to 1.8 liters, use a custom rod, and custom pistons. You could play around with the rod length and stroke a bit, but you would probably end up with a rod to stroke ratio around 1.7:1. Is all of that time and money spent worth it? Probably not. There are advantages like less wear on the cylinders, and increased dwell time at tdc(which has multiple advantages in itself), but in a street application they are negligible.
Trying new things is great, but it rarely turns out the way it's supposed to. Concentrate on getting the clearances perfect, getting your quench area right, balancing, and matching parts that work well together.
05-23-2006, 04:56 PM
#15
0.0 BAR
Join Date: Jan 2005
Posts: 0
Re: rod ratios/ longer rod
Originally Posted by JDMFantasy2K
i actually saw something like that done in a magazine. They de stroked a b16 to 1.5 liters to run it in a certain class and it also made it over square so they could have a crazy high rod/stroke ratio
05-23-2006, 05:58 PM
#16
3.0 BAR
Join Date: Aug 2003
Location: NE-PA
Posts: 4,666
Re: rod ratios/ longer rod
Originally Posted by boost_guy
With a 2mm longer rod you are talking about a .03% decrease in piston speed, and 2% decrease in maximum piston acceleration. That's less than the difference between the B18b and B18c. It's not worth it. 8500 rpm's is not going to be that big of a deal if you select the proper components and build the engine properly.
The only way to really make a dent in piston acceleration is to decrease stroke. Im not completely familiar with Honda B-series engines, but (theoretically) you could use a b20 block, destroke it to 1.8 liters, use a custom rod, and custom pistons. You could play around with the rod length and stroke a bit, but you would probably end up with a rod to stroke ratio around 1.7:1. Is all of that time and money spent worth it? Probably not. There are advantages like less wear on the cylinders, and increased dwell time at tdc(which has multiple advantages in itself), but in a street application they are negligible.
Trying new things is great, but it rarely turns out the way it's supposed to. Concentrate on getting the clearances perfect, getting your quench area right, balancing, and matching parts that work well together.
The only way to really make a dent in piston acceleration is to decrease stroke. Im not completely familiar with Honda B-series engines, but (theoretically) you could use a b20 block, destroke it to 1.8 liters, use a custom rod, and custom pistons. You could play around with the rod length and stroke a bit, but you would probably end up with a rod to stroke ratio around 1.7:1. Is all of that time and money spent worth it? Probably not. There are advantages like less wear on the cylinders, and increased dwell time at tdc(which has multiple advantages in itself), but in a street application they are negligible.
Trying new things is great, but it rarely turns out the way it's supposed to. Concentrate on getting the clearances perfect, getting your quench area right, balancing, and matching parts that work well together.
05-23-2006, 06:58 PM
#18
1.0 BAR
Thread Starter
Join Date: Dec 2005
Posts: 391
Re: rod ratios/ longer rod
WOW! thanks for all the awesome replys... i know you can rev a LS motor to 8500 easily with rod bolts, but I dont feel comfortable doing that and I have pleanty of time to build the motor and have a mechanical engineer/race engine builder helping me for free.... I couldnt ask for more! this is a prime situation to be doing what I am doing
the rod ratio of a stock LS motor is 1.54, with an added 2mm on the legnth of the rod it will give me a rod ratio of 1.71.... not bad in my mind, and yes i know this will hardly slow the piston at all if any (0.03%), but the 2% decrease in maximum piston acceleration is what I'm looking for, this will essentially give me 2% less load on the bottom end of my motor... the amount of stress once put on the bottom end at 8000rpm will now come at 8160rpm..... not much you say? well combine that with the added stronger rated rod bolts, all fresh bearings, dual valve springs, thinner rings, head work, valve job and new head bolts...... and I feel safe revving my LS to 8500
Many would say this is a waste of time..... in fact it may be, but I feel like building a motor and learning as much god damn engine tuning information and theory as I possibally can..... so stay tuned for a complete thread of the build up and how to's
thanks for everyone's comments so far, please keep commenting, positive or negative... I would like to hear may comments... maybe some piston sudjestions?
the rod ratio of a stock LS motor is 1.54, with an added 2mm on the legnth of the rod it will give me a rod ratio of 1.71.... not bad in my mind, and yes i know this will hardly slow the piston at all if any (0.03%), but the 2% decrease in maximum piston acceleration is what I'm looking for, this will essentially give me 2% less load on the bottom end of my motor... the amount of stress once put on the bottom end at 8000rpm will now come at 8160rpm..... not much you say? well combine that with the added stronger rated rod bolts, all fresh bearings, dual valve springs, thinner rings, head work, valve job and new head bolts...... and I feel safe revving my LS to 8500
Many would say this is a waste of time..... in fact it may be, but I feel like building a motor and learning as much god damn engine tuning information and theory as I possibally can..... so stay tuned for a complete thread of the build up and how to's
thanks for everyone's comments so far, please keep commenting, positive or negative... I would like to hear may comments... maybe some piston sudjestions?
05-24-2006, 07:43 AM
#20
1.0 BAR
Join Date: Dec 2002
Posts: 604
Re: rod ratios/ longer rod
they sell longer rods that are designed to be used with special pistons that have the wrist pin moved up. they give you a GSR r/s ratio which is a perfect r/s ratio IMHO for 8500rpm redline. www.theoldone.com -> under components
