Hi all,
I have been lurking here for some time, but finally have my Lexus together and am looking for advice.

Current set-up

OBD 1 NA-t 5spd
TT headgasket/studs
272 cams
550cc inj
340lph fp
Custom FFIM w/4'' TB
MAPCAL V3 piggyback
T67 with mostly ebay hard parts

The car was dyno'd @ 14psi (WG spring)
92 oct pump
colder plugs

even after pulling tons of timing the car was still detonating at higher RPM.
Tuner said either less boost, better gas, or lower compression could possibly sort this out.
I switched over to 93 pump and am still getting detonation.
I see guys on here running stock compression making more power, so I don't believe I need to lower compression or boost.

Any ideas would be very helpful.

Thanks,
Cameron.

 

IMO your pretty brave for going 10;1 compression and 14+psi. I doubt you see more than a handful of guys running more than 14 psi on stock compression unless e85 or stand alone or both.

I believe you need to lower compression or boost, As well im not a seasoned tuner or anything but i was always under the impression the map as a piggyback was not really that great for high boost.

What plugs are you running?

 

mk4 ecu/coils/igniter/maf/map and tell the tuner to fly a kite. but 67 at that boost and ****ty gas is not a good idea. what's compression look like now?

 

thats what i run, aristo ecu with is300 coils for like 14k now DD

 

OP, how much timing are you pulling out of the car, also do you have a aftermarket FPR and have you removed the fuel damper under the intake mounted on the block and rerouted the supply to the back of the rail???

To much timing is bad but to little timing is also really bad??

Colder plug? what plug with #???

 

I thought the TT headgasket got me lower than 10:1

NGK bk 7 cant remember the whole PN

 

If you mean cylinder compression I have not checked. I don't think there was any serious damage done. The MAPECU gets rid of the maf, runs map/iat. I would like to get rid of the distributor though, so coils an a TT ecu may be in my future.

 

upwards of -20 under full boost. No fpr and I know nothing of this fuel damper you speak of. I do not think I am lacking fuel supply though.

The plugs were NGK BKRP7 or something like that. I know they are 7's though.

 

Doesnt the TT hg lower the compression to like 9.2:10? Which would make 14psi completely fine?

 

So how do you know how your fuel pressure is.
-20degrees of timing in full boost????

I run like 14-16 degrees of timing on a built motor on E-85 with more compression than you, as an example.

 

I guess I do not. Just that AFR was hovering in the 12-13 range. So you think it may be a fuel pressure problem? I was planning to do the rewire where you bypass that fuel pump controller or whatever that thing is in the driver side rear interior panel but don't know if that will do anything.

Ill do some research on that fuel damper thing and look into getting a fpr as well.

I took her out tonight and it seemed to be running a little better. I think I finally got all of the 92 oct out of the tank. Still breaks up a little bit under heavy loads (4th gear pull). I may just say F it and get big injectors and go for E85.

 

I believe that is correct. The first response might have been confused, but I am not on stock compression.

 

what happens if you add more fuel up top and bring afr into the high 11s?

edit: question not meant as tuning guidance because I have no tuning ability more of a question aimed towards blk & blu for thoughts because I'm curious if adding more fuel when you have ****ty octane could help cool the cylinder and prevent detonation.

 

^^ Don't think so, it's more like the octane rating..imo

 

Well guess i mis read or it was edited in as you were quoting " I see guys on stock compression making more power" and im wondering where you see this so frequently?
and led me to believe you were using that as a point of reference for your build....

..... so either way your comp is fine.


I run 14 psi on a bb 60-1 all day (and formerly a 67) with no detonation, What exact plugs are you running. Its better to know exactly what you have... not "oh it was something"

also what fuel pump are you running?