Will 7.5:1 and .8bar= Detonation?
07-22-2002 | 08:55 PM
#1
Thread Starter
Instructor
Joined: Aug 2001
Posts: 195
Likes: 1
Will 7.5:1 and .8bar= Detonation?
I'm thinking of purchasing a set of 3.4L Ruf pistons and cylinders which are 7.5:1 compression ratio. I understand that this is slightly higher than stock compression. At .8 bar and on 91 octane fuel (in CA - sux), will I get detonation? I run an andial intercooler.
I'm sorry about this question. I know how despised these types of questions are. Any help will be appreciated.
I'm sorry about this question. I know how despised these types of questions are. Any help will be appreciated.
07-23-2002 | 12:18 AM
#2
Racer
Joined: Jun 2001
Posts: 495
Likes: 0
From: Greensboro NC
t.p.,
I have an early 3.0 that I had converted
to 3.2 @ 7.5 to 1 comp. and I haven't had any
problems with detonation...I ran this setup
with a stock intercooler for a while so my
guess is that you should be fine. Besides,
you'll love the torque incress.
P.S. I run with 1 bar that goes to 1.2 bar
sometimes
I have an early 3.0 that I had converted
to 3.2 @ 7.5 to 1 comp. and I haven't had any
problems with detonation...I ran this setup
with a stock intercooler for a while so my
guess is that you should be fine. Besides,
you'll love the torque incress.
P.S. I run with 1 bar that goes to 1.2 bar
sometimes
07-24-2002 | 07:50 PM
#3
RL Technical Advisor
Joined: May 2001
Posts: 11,871
Likes: 66
From: Portland Oregon
T.P.
Please don't apologize about the question,...its really a good one.
First, you may use a 7.5:1 CR with stock boost on 91 octane fuel. Just use some unleaded race gas (50/50) should you go to the track.
FWIW, stock 930's will detonate in hot weather on 91 or 92 octane fuels so be careful. Do NOT raise boost pressure levels unless your pocketbook is well stocked with $$$$$ as this is the surest way to destroy your new P/C's in very short order.
Personally, I'd consider installing twin-ignition to get some reasonable detonation margins.
Pete in Ohio can get fuels that are not available on the West Coast (aside from race gas), and boost levels over 1 bar will truly shorten the life of these engines.
Please don't apologize about the question,...its really a good one.
First, you may use a 7.5:1 CR with stock boost on 91 octane fuel. Just use some unleaded race gas (50/50) should you go to the track.
FWIW, stock 930's will detonate in hot weather on 91 or 92 octane fuels so be careful. Do NOT raise boost pressure levels unless your pocketbook is well stocked with $$$$$ as this is the surest way to destroy your new P/C's in very short order.
Personally, I'd consider installing twin-ignition to get some reasonable detonation margins.
Pete in Ohio can get fuels that are not available on the West Coast (aside from race gas), and boost levels over 1 bar will truly shorten the life of these engines.
07-24-2002 | 09:11 PM
#4
Thread Starter
Instructor
Joined: Aug 2001
Posts: 195
Likes: 1
Steve,
I've heard that twin ignition is no longer an option as Bosch has discontinued the requisite 12 nipple distributor cap. Is this truae? I've also heard that a twin-distributor option is no feasible on a 930.
I've heard that twin ignition is no longer an option as Bosch has discontinued the requisite 12 nipple distributor cap. Is this truae? I've also heard that a twin-distributor option is no feasible on a 930.
07-24-2002 | 09:54 PM
#5
RL Technical Advisor
Joined: May 2001
Posts: 11,871
Likes: 66
From: Portland Oregon
[quote]Originally posted by t.p.:
<strong>Steve,
I've heard that twin ignition is no longer an option as Bosch has discontinued the requisite 12 nipple distributor cap. Is this truae? I've also heard that a twin-distributor option is no feasible on a 930.</strong><hr></blockquote>
T.P.
Twin-ignition is always an option,...it simply depends upon which way to do it,...
Bosch did indeed discontinue the manufacture of the RSR caps & rotors and for Turbos' this was very tough as thats the easiest & best way to do that. I've found a few new caps & rotors in Europe and hopefully we'll be able to do a few more, soon.
The 964 dual distributor will not fit on a Turbo so that, unfortunately is not an option.
I'm no fan of the current crop of inexpensive crank-fire ignitions so I do not use them here.
If this is something that you are seriously considering, please contact me directly.
<strong>Steve,
I've heard that twin ignition is no longer an option as Bosch has discontinued the requisite 12 nipple distributor cap. Is this truae? I've also heard that a twin-distributor option is no feasible on a 930.</strong><hr></blockquote>
T.P.
Twin-ignition is always an option,...it simply depends upon which way to do it,...
Bosch did indeed discontinue the manufacture of the RSR caps & rotors and for Turbos' this was very tough as thats the easiest & best way to do that. I've found a few new caps & rotors in Europe and hopefully we'll be able to do a few more, soon.
The 964 dual distributor will not fit on a Turbo so that, unfortunately is not an option.
I'm no fan of the current crop of inexpensive crank-fire ignitions so I do not use them here.
If this is something that you are seriously considering, please contact me directly.
08-04-2002 | 02:02 AM
#6
Race Car
Joined: Aug 2002
Posts: 3,811
Likes: 2
From: Singapore
Going to 7.5 compression is a very good move. Makes your car take of like a V8 from the traffic light. However octane must be higher. I guess you'd must go for twin plugging to play safe. The Ruf 3.4 with 7.5 compression is what I have on. Good thing here in Singapore they offer 98 octane from any regular or all gas stations.
08-04-2002 | 02:04 AM
#7
Race Car
Joined: Aug 2002
Posts: 3,811
Likes: 2
From: Singapore
I forget to mention, just keep boost under 1 bar. Nothing more. I'm at 0.9 bar of boost with an additional oil cooler for extra cooling. You have to take these measures when going higher compression for better cooling.
