3 Liter Turbo Registry
#1216
just went to my stock and picked 4 random camshafts of the box - 100% stock NA engines with soft springs... so I'm sure I don't want to put more load to them
I am and appreciate your input - but don't you think thousands of 951 engines are also real life experiences? thats exactly what they did - original turbo springs are softer as NA springs... and at no point the force on turbos valves is lower as on NA springs
I took all these measurements and trials because I knew the standard springs are not working (from the first 16V engine I build 3 years ago) but the car owner wanted it that way...
I am and appreciate your input - but don't you think thousands of 951 engines are also real life experiences? thats exactly what they did - original turbo springs are softer as NA springs... and at no point the force on turbos valves is lower as on NA springs
I took all these measurements and trials because I knew the standard springs are not working (from the first 16V engine I build 3 years ago) but the car owner wanted it that way...
#1218
Very good point! Supercharged engines don’t have any issues on outlet valves as they directly blow out to atmosphere, turbos create a backpressure of 1,5-2 times of the boost, means 1 bar boost loads 1,5-2 bar pressure to the outlet valves
#1219
https://www.lindseyracing.com/LR/Par...VESPRINGS.html
here is another good explanation.
You are welcome to try your theory, but it can be an expensive try & error.
here is another good explanation.
You are welcome to try your theory, but it can be an expensive try & error.
#1220
I think everyone is getting confused by your explanation, the graph says it all. Seat pressure is higher but your full lift numbers are close to the same. By using a taller spring with a lower spring rate the additional compression bumps up the seat pressure. But because the spring has a lower rate by the time you’re at full lift the pressure hasn’t increased as dramatically as it would be if you had just replaced it with a stiffer spring. Bit of an odd way to think about it as most spring manufacturers will specify an installed height and pressure along with its rate and max travel at this setting and you just chose one to suit.
I would still be accounting for the additional boost pressure.
I would still be accounting for the additional boost pressure.
#1221
Addict
Rennlist Member
Rennlist Member
So... Which springs? Any recommendations? I intended to use stock na but I'd like to boost slightly over .5 bar some day.
#1222
Three Wheelin'
What cam or cams are you planning on using that would be a good start for which springs. Also if using stock springs new or 30 years old springs?
My first 3 liter 8 valve build I used 20 year old stock 951 springs in a 2.7 head and had a shop rebuild the head to specs and with only 16 psi the head rattled a lot from valve float under full boost/ load and It was bad so I pulled the head a few months later and went with titanium shims to make the springs more preloaded and the float went away!
My first 3 liter 8 valve build I used 20 year old stock 951 springs in a 2.7 head and had a shop rebuild the head to specs and with only 16 psi the head rattled a lot from valve float under full boost/ load and It was bad so I pulled the head a few months later and went with titanium shims to make the springs more preloaded and the float went away!
Last edited by boost feen; 04-06-2023 at 10:49 AM.
#1223
Addict
Rennlist Member
Rennlist Member
I have stock 968 cams and intend to use variocam.. What's the experience with variocam + turbo? Any sense in controling it with standalone?
#1224
#1226
I am about to add my build to the list, any helpful thoughts on compression ratio would be appreciated. It looks like most builds are from 8:8 to 8:1, any specific benefits to either side of the scale?
#1227
Context, 968 block and crank, Darton dry sleeve, 106mm JE Forged pistons, Carrillo rods, 2.7L head Ferrea valves, LR 3Lcam. Currently planning on LR Super 65 BB with 951 header and crossover, 3" exhaust.
Last edited by alengyel; 06-25-2023 at 11:28 PM.
#1228
Rennlist Member
#1229
Broadfoot is installing the sleeves, Ive see multiple sources for wet sleeves including a set on eBay now.
#1230
Rennlist Member
If you're going to all that trouble to build a 3lt motor you could look to a more modern turbo.
The following 2 users liked this post by 333pg333:
alengyel (06-29-2023),
DasSilberWedge (10-09-2023)