Best balance of boost and compression for a DD
06-05-2007, 11:56 AM
#34
Originally Posted by Tootall
when's it coming back, I like reading up on stuff like this.
06-05-2007, 11:33 PM
#37
Originally Posted by 1slow01Z71
Hey, mine too! 
Originally Posted by Stoichiometric
What kind of timing and iats were you seeing when you had detonation at 6lbs? The longer stroke makes detonation more likely to occur.
06-06-2007, 06:44 AM
#38
Good choice on the CR. I'd lean towards 9 myself, with your ambient temps. The head choice is a great one, IMO. It's what I would've purchased had I known Richard when I did mine. Then there's the 317 vs LS6 vs 5.3 heads thing -- IMO the 317s are the best for turbos 
What was your old cam? If I could make a recommendation, I'd choose a cam in the 230s with a reverse split to feed the turbo better. I'd also choose a wide lsa (e.g. 117 or 118) to help reduce cylinder pressure and reduce the effective compression. The reason I suggest this is from my experience in 100* summers here and a forward split cam with a 114. It was much rougher and had significantly more knock. Moving to the reverse split and 115 I'm running now, eliminated all the KR problems I was seeing in the summer, as strange as that sounds since they were nearly identical except for the pattern.
Richard knows his knitting, though, and has a lot more experience with multiple cams, heads, motors, etc. I'd love it if he'd drop in this thread and explain the cam suggestion.
Anyway, here's to you gettin the beast back on the road
What was your old cam? If I could make a recommendation, I'd choose a cam in the 230s with a reverse split to feed the turbo better. I'd also choose a wide lsa (e.g. 117 or 118) to help reduce cylinder pressure and reduce the effective compression. The reason I suggest this is from my experience in 100* summers here and a forward split cam with a 114. It was much rougher and had significantly more knock. Moving to the reverse split and 115 I'm running now, eliminated all the KR problems I was seeing in the summer, as strange as that sounds since they were nearly identical except for the pattern.
Richard knows his knitting, though, and has a lot more experience with multiple cams, heads, motors, etc. I'd love it if he'd drop in this thread and explain the cam suggestion.
Anyway, here's to you gettin the beast back on the road
06-06-2007, 10:16 AM
#39
Launching!
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thanks for the hot thread man .
but a important question for me .
why do u detonation on 8 boost !!! this is wierd to me i thought ur cr was 9 something !!! r ur feul enough !!
im planning to add a twin turbo or single turbo on my car but u scared me alot compression ratio is 9 and u have a detonation !! !!!
but a important question for me .
why do u detonation on 8 boost !!! this is wierd to me i thought ur cr was 9 something !!! r ur feul enough !!
im planning to add a twin turbo or single turbo on my car but u scared me alot compression ratio is 9 and u have a detonation !! !!!
06-06-2007, 11:11 AM
#40
FormerVendor
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This engine had oil consumption problems, a serious cause for detonation. Also the pistons had a perfectly round dish and they're not quench friendly.
I think when added together these factors led to the detonation problem. This go around we're backing the cr down slightly.
As far as cam split is concerned, I'm not a big fan of reverse split grinds because the off boost response suffers slightly and EGT's are elevated due to the early closure of the exhaust valve. Street driving offers many challenges and compromises and in Chris's case I feel his new grind will balance off boost driveability and max boost performance. I did make an adjustment in the final decision for his cam. I tightened up the split to within 2º. This cam will combine a respectable idle with nice street manners and still allow for a broad power band that will pull beyond 6000rpms.
Richard
I think when added together these factors led to the detonation problem. This go around we're backing the cr down slightly.
As far as cam split is concerned, I'm not a big fan of reverse split grinds because the off boost response suffers slightly and EGT's are elevated due to the early closure of the exhaust valve. Street driving offers many challenges and compromises and in Chris's case I feel his new grind will balance off boost driveability and max boost performance. I did make an adjustment in the final decision for his cam. I tightened up the split to within 2º. This cam will combine a respectable idle with nice street manners and still allow for a broad power band that will pull beyond 6000rpms.
Richard