rwdawg2 Posted April 22, 2009 Author Share Posted April 22, 2009 Alright guy with unlimited money. Just trying to keep down detonation is all. Not trying to choose a particular CR ratio. Just precautionary measures. I do not want all this money (forged pistons, motor and head work) to shoot down the tube because I could have spent a LITTLE extra money on a better seal (i.e. headgasket). Thanks for your input though. Quote Link to comment Share on other sites More sharing options...
jc052685 Posted April 22, 2009 Share Posted April 22, 2009 going off your sig you are shoooting for 300hp and you built a forged short block. Yikes...for someone with no money sure seams you have alot of extra. Quote Link to comment Share on other sites More sharing options...
slown280z Posted April 22, 2009 Share Posted April 22, 2009 You can keep detonation down with proper fueling and spark. I'm trying to save you money, so that you don't buy a $200 gasket then melt a piston/cook a bearing. People have been getting away with turboing 240z's and their 9:1 (I think) CR for ages. You just have to set your goals and choose parts accordingly. Do it once and do it right! You'll save money in the long run. Quote Link to comment Share on other sites More sharing options...
woldson Posted April 22, 2009 Share Posted April 22, 2009 Have you considered meth inject? Or ceramic coatings? Quote Link to comment Share on other sites More sharing options...
rwdawg2 Posted April 22, 2009 Author Share Posted April 22, 2009 Slown280z - I'm planning on running megasquirt or SDS not sure yet. So hopefully with that I will be able to have proper fuel and spark. Also knowing that people have gotten away with 9:1 CR and forced induction eases me a bit. Thank you. woldson - I have not thought about either. Don't know much about them. Quote Link to comment Share on other sites More sharing options...
neotech84 Posted April 22, 2009 Share Posted April 22, 2009 Just a side note....... If the Fel-pro gaskets are the Perma Torque series, those are Multi Layer Steel (MLS). so you are set Quote Link to comment Share on other sites More sharing options...
WizardBlack Posted April 22, 2009 Share Posted April 22, 2009 Also knowing that people have gotten away with 9:1 CR and forced induction eases me a bit. The Mitsu EVO has 8.8:1 and runs 21 psi from the factory. That's with the "idiot/kid" factor built in. As you build an engine, it's usually gets less prone to detonation. I personally view 9:1 as an ideal boost compression ratio. Quote Link to comment Share on other sites More sharing options...
WizardBlack Posted April 23, 2009 Share Posted April 23, 2009 Just a side note....... If the Fel-pro gaskets are the Perma Torque series, those are Multi Layer Steel (MLS). so you are set That is interesting. I will have to look at mine. It's sitting on the block while I finish my Isky parts install on the head. It is definitely stiff enough to be MLS. Quote Link to comment Share on other sites More sharing options...
slown280z Posted April 23, 2009 Share Posted April 23, 2009 The Mitsu EVO has 8.8:1 and runs 21 psi from the factory. That's with the "idiot/kid" factor built in.As you build an engine, it's usually gets less prone to detonation. I personally view 9:1 as an ideal boost compression ratio. Head, piston, and cam choices have a huge influence on what an engine can "get away" with (of course, an efficient turbo can make a difference too, as to not be a hairdryer). You'd have nice off boost drivability and a lower boost threshhold with a 9:1 CR L engine, but you won't be able to hit as high of a peak horsepower as a lower CR L. Sometimes that doesn't matter, as that probably wasn't the goal of that engine. There was a thread on here recently that spoke that you can "make up" the horsepower difference of one compression point with 1 PSI of boost, and that you'd be able to run a higher amount of boost in the end, but in turn, give up a few RPM in your boost threshold and have not as peppy off boost response. It's all a balancing act to your wants and needs! Quote Link to comment Share on other sites More sharing options...
rwdawg2 Posted April 24, 2009 Author Share Posted April 24, 2009 Thank you guys a ton. You all are full of helpful information. I think I can confidently build this motor, lol. Just a little worried you know. I'll keep you updated. Thanks again Quote Link to comment Share on other sites More sharing options...
WizardBlack Posted April 25, 2009 Share Posted April 25, 2009 Thank you guys a ton. You all are full of helpful information. I think I can confidently build this motor, lol. Just a little worried you know. I'll keep you updated. Thanks again If you are new to tuning turbos and you don't have anyone around to help you with tuning it, dope the gasoline with some race fuel. Get the estimated octane up about 4~6 points (as in, 91->96 or 97) and tune it. You will have a much wider margin of safety at pump gas boost levels and pump gas A/F ratios. After you get fuel maps dialed in (and you use a timing map from a proven car with a few degrees knocked off everywhere), start letting the octane drop and tweak the whole map richer a percent or two (to adjust for the drop in octane; higher octane runs a bit richer) and you will be pretty safe. Leave the rest of the timing on the table until someone can tune with you to get the last bit. Quote Link to comment Share on other sites More sharing options...
z-ya Posted April 25, 2009 Share Posted April 25, 2009 If you are new to tuning turbos and you don't have anyone around to help you with tuning it, dope the gasoline with some race fuel. Get the estimated octane up about 4~6 points (as in, 91->96 or 97) and tune it. You will have a much wider margin of safety at pump gas boost levels and pump gas A/F ratios. After you get fuel maps dialed in (and you use a timing map from a proven car with a few degrees knocked off everywhere), start letting the octane drop and tweak the whole map richer a percent or two (to adjust for the drop in octane; higher octane runs a bit richer) and you will be pretty safe. Leave the rest of the timing on the table until someone can tune with you to get the last bit. This is all well and good, as long as you continue to run race fuel. Eventually you will want to run pump gas, and who knows, you may have detonation. If you like changing head gaskets, this is the way to go. Find a good dyno shop, and spend a couple hundred on dyno time. It is more than worth it. Pete Quote Link to comment Share on other sites More sharing options...
WizardBlack Posted April 26, 2009 Share Posted April 26, 2009 This is all well and good, as long as you continue to run race fuel. Eventually you will want to run pump gas, and who knows, you may have detonation. If you like changing head gaskets, this is the way to go. Find a good dyno shop, and spend a couple hundred on dyno time. It is more than worth it. Pete How is that going to blow HG's? Are you sure you read everything I stated? I directly told him to taper it off of higher octane. Obviously having a pro tune it is the way to go, but if you can't do a basic tune on your car, you shouldn't have a standalone on it in the first place, IMHO. Especially if it's a DD. Mark Quote Link to comment Share on other sites More sharing options...
z-ya Posted April 26, 2009 Share Posted April 26, 2009 Detonation will blow the head gasket. I guess my point is to just start with the fuel you plan on running on a regular basis. You can simulate a higher octane fuel with conservative timing and boost levels. Get the AFRs in the 12:1 range under boost. Any signs of detonation, let off. Have a friend listen for detonation. Back off the timing a couple degrees and do another pull. Doing this kind of tuning while driving is not easy (or safe). Finding a nice long stretch of road uphill is not easy. The dyno will simulate this for you. Pete Quote Link to comment Share on other sites More sharing options...
dhartig Posted April 27, 2009 Share Posted April 27, 2009 I think z-ya and WizardBlack are both saying take a conservative approach to dialing in your tuning. We can get pump gas at 94 octane here in Canada so we don't have to guess at a mixed fuel octane level. My plan is to start rich and then use the AFR to dial in the tune. Then add a few more psi of boost and slowly repeat until it all looks good. Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.