Building an all motor LS motor. My question is how high of compression can you go with LS motor that still reliable under road race condition?

If so which company makes good pistons for the highest compression LS motor can hold for road racing?

thank you for any feed back!

 

need little help here!

 

Pretty much as high as you wanna go if you wanna run race gas only and just put some ctr pistons they give plenty of compression.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by jdm92civichb &raquo;</TD></TR><TR><TD CLASS="quote">Pretty much as high as you wanna go if you wanna run race gas only and just put some ctr pistons they give plenty of compression.</TD></TR></TABLE>

But how much can LS bottom end hold up? It's not as high as I want...it is how high can I go. Yes, if just running race fuel what high of compression can I go before the LS block "gives up"?

 

It depends on the rest of your engine build. Undercamming = bad.

 

spend the money and get a set of forged pistons. Importbuilders.com best pricing plenty to choose from

 

how much compression do your cams need? or you think the more the merrier?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by mmuller &raquo;</TD></TR><TR><TD CLASS="quote">how much compression do your cams need? or you think the more the merrier?
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Regardless which cams I will be using. I just wondering how much compression can a LS block hold before it go "bad"? So far I have seen some as high as 12:1 compression ratio, but is it save for road racing? Or I can get even higher then that to get even more power out of little 1.8 LS?

 

It is still a question of cams..

your going to be hard pressed to fit cams that require 12:1 or higher CR

404's start getting overcammed after you reach 11.5:1 , and the 405b's require massive modifications to the head.

 

Ok, I guss I should ask the question like this: What is the highest compression can LS (B18A/B) motor hold and match which cams for the best NA motor without TOO much modification or unreliable modification?

Thank you for any input!

 

Crower 404's with 11.1 or 11.5.1 or you can go higher comp but u might need some custom ground cams

 

what about stock cams and set of ctr pistons or gsr pistons and thin layer head gasket

 

What type of road racing will you be doing? Honda Challenge rules stipulate that OEM Pistons must be used. In that case CTR pistons are your best hope, as they will yield around 12.2:1 compression.

As some have mentioned you need to factor in what type of cams you will use and the extent of headwork you are willing to have done. I have seen 13:1 run on an LS with Crane #20 cams. If you are looking at running large cams, and high compression, consider looking into Crane #20's, Crower 405's, and Crower 405A's. The 405A's require head modification, which to me seems a lil extreme once you find out what all has to be done.

You need to figure out what you want to accomplish, and what your racing sanction allows. Then play around with some numbers to see what cam and compression configuration you want to run. They need to compliment each other. Remember too much compression is never a good thing. You will hit a point where all that compression will work against you and harm performance.

 

The more compression the more efficient the engine Period. Prime examples of this are diesel engines that have upwards of 17:1 compression and gobs of torque.

It is far worse to overcam an engine than to undercam one as overcamming drops the dynamic compression. Less compression drops the torque and subsequently the power suffers. Higher compresison increases the cylinder pressure which pushes on the piston with more force which translates to more torque across the board. More torque means more horsepower.

The trick is to run as high a compression ratio as possible without any detonation or retarding the hell out of the ignition timing. 11:1 is pretty safe for the street. Assuming that you tune it well you can go to 12:1 or more pretty easy for the street on 91 octane. Race gas is another matter.

Pirate

 

Diesels do not make alot of torque per unit of displacement. The reason diesels have such high compression (usually 20 and up) is that is the only way a spark-ignition motor will run. Any less compression than that and the fuel will not ignite when it is injected into the chamber. People think that diesels are "torquey" because they do not rev that high. If you add a turbo to the diesel--well that is a different story. The reason diesels don't make much power is because they do not have throttle plates. Engine speed is 100% controlled by how much fuel is injected into the CC. At low rpm, diesels may have air/fuel ratios of 60:1!!

 

We have run 12.5-1 on LS road race motors. At .5mm and 1mm over with no problems. You just need to make sure you have good cooling and keep the water temp below 185F. They run better ther also.

 

sry to jack the thread, but hw major is the modification needed to fit the 405a cams in the ls head?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote &raquo;</TD></TR><TR><TD CLASS="quote">
The more compression the more efficient the engine Period. Prime examples of this are diesel engines that have upwards of 17:1 compression and gobs of torque.
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Yeah... no...

Think about cylinder pressures as compression increases, think about how that can effect velocity of the piston. Think about how high cylinder pressures reducing the velocity of a piston on the compression stroke would be a bad thing.