ae85 fiend Posted February 12, 2013 Share Posted February 12, 2013 Hey guys, So i'm building a 7agte for my ae85. Just saw SamQ's rough estimate on CR's with the different 4ages/ TRD HG's/ 7A bottom ends: http://s-86.com/s-cr-chart.html I plan on running 20v silvertop pistons, my forged 7afe conrods, and the 7a bottom end. which supposedly gives me a CR of 11.5... I'm just curious as to what would be the benefits/ negatives of running a turbo'd engine with a higher CR like that? As from what i've read online, everyone that turbo's engines seem to be wanting in the 8's/ low 9's? And, if it is that bad to be running a 11.5 Compression ratio on that type of engine, what would be the best way to lower it, apparently changing the headgasket would be the easiest, but what else? I've read somewhere about decking the block or something? And what sort of CR would be the best for both responsiveness and driveability? somewhere like 10.1 ish? If you can actually make heads or tails about what I wrote, any help would be greatly appreciated. Cheers, Liam Quote Link to comment Share on other sites More sharing options...
UTERUS Posted February 12, 2013 Share Posted February 12, 2013 I dunno if they fit, but you could use gze pistons. Just means it's now an interference engine if you meet mr snappy cambelt. he's a dick btw Quote Link to comment Share on other sites More sharing options...
Escorto. Posted February 12, 2013 Share Posted February 12, 2013 11.5:1 cr is too high for an NA engine (depending on cam) let alone a churbro one. 8:1 would be what your after. Maybe even lower. You wont be able to get that much with just a HG Quote Link to comment Share on other sites More sharing options...
Llama Posted February 12, 2013 Share Posted February 12, 2013 Different pistons would be your best bet, that or a crank with less throw. You could possible get the chamber machined out, or build up the head/block somehow? No idea on that tbh. Quote Link to comment Share on other sites More sharing options...
Yowzer Posted February 12, 2013 Share Posted February 12, 2013 It all depends on how much boost ya wanna run. 11.5 is way too high for any sort of boost, without running on some ultra-high octane juice like race gas / av-gas / methanol Quote Link to comment Share on other sites More sharing options...
sentra Posted February 12, 2013 Share Posted February 12, 2013 2 Quote Link to comment Share on other sites More sharing options...
ae85 fiend Posted February 12, 2013 Author Share Posted February 12, 2013 Mhmmm... Well that sucks, there goes my budget for the engine if I have to buy new pistons, yeah, I was reading about using GZE pistons, but like you said, it would become an interference engine unless it was flycut? Which then makes it supposedly 'safer' to use Quote Link to comment Share on other sites More sharing options...
Yowzer Posted February 12, 2013 Share Posted February 12, 2013 As for lowering compression. Crank with shorter stroke will lose you capacity. And good luck finding one. Slightly shorter conrods is an option, but expensive. Best bet is either get your pistons machined down a bit to drop the compression (get it done by someone who knows what they are doing as pistons can play a big part in the swirl in the chamber) or swap them for some other pistons. You may find ZE pistons are dished enough to allow valve clearances on the 20V head, but check beforehand. Quote Link to comment Share on other sites More sharing options...
xsspeed Posted February 12, 2013 Share Posted February 12, 2013 Jump on toyspeed man, and do a search, its covered there lots. IIRC most use 4agze pistons. Problem with the 7a rods is they are long and skinny and like to bend Quote Link to comment Share on other sites More sharing options...
Yowzer Posted February 12, 2013 Share Posted February 12, 2013 Aren't they interference engines anyway? Quote Link to comment Share on other sites More sharing options...
xsspeed Posted February 12, 2013 Share Posted February 12, 2013 I dont think the gze's are? Quote Link to comment Share on other sites More sharing options...
ae85 fiend Posted February 12, 2013 Author Share Posted February 12, 2013 It all depends on how much boost ya wanna run. 11.5 is way too high for any sort of boost, without running on some ultra-high octane juice like race gas / av-gas / methanol Was looking at about 14psi, but realistically probably 8-10, probably 8 to start off with though. Quote Link to comment Share on other sites More sharing options...
sentra Posted February 12, 2013 Share Posted February 12, 2013 http://forums.evolutionm.net/evo-dyno-tuning-results/603511-781hp-41lbs-e85-mustang-dyno-3rd-gear-pull.html /will leave now Quote Link to comment Share on other sites More sharing options...
Yowzer Posted February 12, 2013 Share Posted February 12, 2013 14psi at a rough guess would want 8-9: compression to be usable on pumpgas. Cams and stuff do play a big part in what you can get away with though, way beyond my current knowledge. 1 Quote Link to comment Share on other sites More sharing options...
Spencer Posted February 12, 2013 Share Posted February 12, 2013 That cars running E85 egg Quote Link to comment Share on other sites More sharing options...
Yowzer Posted February 12, 2013 Share Posted February 12, 2013 Everything should be running E85 Quote Link to comment Share on other sites More sharing options...
Spencer Posted February 12, 2013 Share Posted February 12, 2013 Yea if you want to fill up every 10min, rather run Methanol when it comes to alchy, E85 only makes sense if its legal in your race class or whatever So only blacktops are inference factory yowzer, he has some decent rods xssteve. I would aim for somewhere around 10:1 for a nice street set-up which puts you in the relms of the late model ZE pistons with your bottom end (if you believe that chart). Don't think he is ever on here but baz from here http://www.mrpltd.co.nz/aboutus.html is who I would be asking all these questions Quote Link to comment Share on other sites More sharing options...
JoKer Posted February 12, 2013 Share Posted February 12, 2013 but does it have singh grooves? Quote Link to comment Share on other sites More sharing options...
sentra Posted February 12, 2013 Share Posted February 12, 2013 close enough spence???????? edit just saw reponce highcomp + fi is the greatest thing since 5m i drive around in hysterics at only 10:1/14psi and have made it lifes mission to spread the word/create controversy Quote Link to comment Share on other sites More sharing options...
Spencer Posted February 12, 2013 Share Posted February 12, 2013 Fuck man I'm all for high comp turbo goodness, but that example is on a super forgiving fuel, forged pistons, decent cams, good tune etc. A bit different to this guys budget build? 1 Quote Link to comment Share on other sites More sharing options...
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