gatorhead

iTrader: (4)

I now know how a tennis ball feels!
What are the SCR/DCR limitations on a LTX motor with 93 pump gas.
I have sooo many different answers I do not know which to believe, and I am looking for any concrete evidence of said limits.

I have 68 cc 190 AFR's and I wanted compression to be on the higher side, the only way I could achieve that, without excessive milling,
was to utilize a domed piston.

I had everything in check UNTIL I called for a custom ground cam and was told that it would not work! That the LTX manifold does not like a domed piston and that the compression was too high. I was told by said grinder that 11.5:1 was the max ratio I should run with pump gas and with a flat top only.

I know that chamber design, piston design, scr/dcr and temperature play a major role in alluding detonation.Everything that I have come across is written for traditional sbc so my question is how does the reverse flow help with detonation and how much of a cushion does it really allow us to run?

Thanks in advance for any and all input
Jack

thebufenator

iTrader: (2)

My static is about 12.2 - 1
dynamic is about 9.17 - 1

Seems fine.....still working out the bugs. No knock on 8 month old 93 octane

transamws6_97

iTrader: (5)

i don't have any concrete evidence but I've heard of guys on this forum running 13.5:1 on 93 gas...cam selection and tuning have a lot to do w/ it

gatorhead

iTrader: (4)

From what I had gathered to this point was that 13.8:1 was the threshold. I know that tuning is key as well as intake closing ABDC. What I am trying to distinguish is the relevance in temperature reduction due to reverse flow cooling as compared to sbc. This seems to be the key to the answer that no one has been able to show. I have talked personally with several people running much higher compression than what I am trying to achieve, however I am as of now limited to a domed piston and that is more prone to detonation than a flat top.

infinitebird

iTrader: (11)

there was just a thread on this: https://ls1tech.com/forums/lt1-lt4-modifications/876242-highest-compression-still-run-93-octane.html

I would assume you could go high 12s at least regardless of piston type, other people have run domed pistons with high compression. 13.x is starting to get up there and you might need to consider things more carefully.

gatorhead

iTrader: (4)

Thanks and yeah I read that thread, as I also performed seraches at EVERY forum and read every thread available.
As I said in my first post I was clear on my goals, my build, my spec etc. UNTIL I tried to get a custom ground cam. Then I was redirected and have been scarmbling to get a scientific answer before I watch the 10k+ I have into the build go awash.
There are alot of members here who know me or know of me from other boards and I too am guilty of throwing out a number because it is regualrly available and seems acceptable.However more than a few builders that are LT1 versed do not agree with it.
I just was hoping that there was a document somewhere that my tired eyes have missed that says the accepatble SCR/DCR for a reverse flow cooled motor is xxxx because the chamber temperature allows xxx amount of increased compression. I FULLY UNDERSTAND the aspects of valve event timing, sweep of the piston, cylinder pressure, swirl, atomization, flame propagation and every other thing about a motor. I have read more than any normal person should lol, and it all pertains to a traditional sbc. Using those theories I incorporated a build based on the factory releases of a traditonal sbc and the ltx motors and noticed that there is almost a two point difference in the acceptable comp ratios.
Maybe that makes sense to you, maybe I am just paranoid and reaching. The fact remains that I still have not seen the answer

speed_demon24

iTrader: (6)

DCR is just another tool for the internet cam experts to claim about mastering...