hello all. I have a 1992 lexus sc300 with a r154 5 speed swap. also have xs power headers and b pipe with no catalytic converters. my whole car is catless. also have injen intake, (bought with the car.) other than that it is factory and bone stock. all cylinders are above 150 psi on compression dry test.
i'm looking to go to midnight mayhem next Friday or Saturday to see what my quarter mile times are. well I heard from a coworker that I should bump up my timing a little to get a little bit better power or faster times. I was wondering if this is ok? maybe 2 or 3 degrees more if I go with 91 octane or maybe 5-9 degrees if I use higher octane fuel.

http://www.mkivsupra.net/vbb/showthr...gnition-Timing
I was looking at this forums and post number 7 says it could work, but I do more research than just, "oh I saw this and now I wanna try it," BOOM goes engine.

 

often times on the stock ecu you end up loosing power when doing that. you can maybe try it with 2 more degrees as the base timing is 10 plus or minus 2 degrees.

say your base is 10, you bump it up to 12 to see what it does. it might pick up a hair more power, emphasis on might.

now you say hey maybe that worked let me try 4 degrees so 14 base timing, what happens is that theoretically speaking more timing more power, but that isn't the case cause with 4 extra degrees across the board and pump gas, you are more likely to knock at some point. when the ecu feels knock at any point, I can assure you it pulls more than 4 degrees back out across the board, so ultimately you end up loosing power as soon as the ecu picks up any knock compared to leaving it alone. one could counteract this with better fuel as, but 91 is not the better fuel. adding some e85 might help or use water/meth injection, race gas would certainly do the trick as well but might be overkill.

also past a certain amount of optimal timing, the motor does not pick up more power, in fact it starts to drop off a little while increasing cylinder temps and pressures, and a hair past that it knocks severely. this is why you normally find where it starts to knock, and then back off several degrees, not just leave it there.

my point is that turning the dizzy to get you a few more degrees doesn't always result in more power. you can maybe get a positive result with 12 on the stock ecu with some good gas, possibly even 14+ with some race gas mixed in, but not with pump gas. I am not saying it wont run at 14 on pump gas, it will run fine, it just might not be "better" than before. some people swear by it, some people are skeptical, my advice would be if you have to try it only do a couple degrees at a time, and try not to go past 14, 12 is the most likely point that could net a positive effect, and is still within the stock range.

you need to remember that as soon as you pull the jumper to set timing, the ecu adds in its extra advance, so that 14 suddenly becomes like 18+ degrees at idle.
A gte motor could do that at idle and keep on ticking, but a GE motor with higher compression is going to have knock and that ecu is going alter the timing trim.

 

ok. got it ali. thanks. yeah I was thinking maybe trying race fuel but don't know if its worth it. I might try 2 degrees if I don't like my first 2 runs on stock.
if anything i'll go the second day with some race fuel and up it to 14 but just for 1 maybe 2 runs. bad thing is though that if I don't like 14 degrees and I drop it back down, then i'll have race fuel on base time; I don't think my engine will like that very much.
what do you think?

 

I dont think 12 should be much of an issue even on 91. I would try that first and see if its even worth trying for 14.
high compression motors only respond well to more timing up to a point, if you had a 9:1 or 8.5:1 those motors will eat up more timing, but stock they are 10:1.
you could also put a gallon or so of e85 in there to a full tank of gas, that should raise the octane and since you aren't boosted you shouldn't run into any leaning out issues on top. I wouldn't over do it though on the e85. there wouldn't be anything wrong with race gas and regular timing, except the wasted cost of the race gas I think.

let us know how it goes though def interested to hear the results.

 

alright. i'll try the race gas on base timing, then 12, then 14, then more if I feel its fit. i'll post time slips and see what that does. I would like to do a dyno day with that as well but haven't gotten around to that yet.

 

you had me thinking again on the running race gas on a normal engine, and this seems like a good read.
http://www.badasscars.com/index.cfm/...rod/prd427.htm
you were onto something about possibly loosing power with race gas. it seems maybe you may want to run some type of mix so you don't raise the octane too much. stock na is 10:1 so it should respond ok but read this article and see what you think. im sure if you figure out the right mix for your setup and the right advance it will help you put down better times.
I know they run it on the turbo motors all the time, just not sure what the best fuel is to get a n/a down the track but I am familiar with raising octane. I occasionally add a gallon of e85 to my pump gas and the car seems to like it. probably loosing mpg's but thats not why I do it.

 

yeah. I had read an article like that a couple years ago and that's why I said race fuel wouldn't be happy under base timing. but I wasn't planning on 110 octane, I new that was too high for me. even 96, (if they make 96) would be ok. I read a magazine a couple years ago about 93 being the best octane out there, I don't remember fully but i'll try and find it and post it.
anyways, yeah i'll try anything that's above 91 but nowhere above 100. thanks in advance ali.

 

You can mix 100 + the premium grade available to you. Based on the % you use you should be able to get a homemade mix of an octane rating.

If you're not running a wideband O2 sensor, I would consider it.