Looking for Opinions on Cam Upgrade, Pauter Rods, Big Valve Head
10-23-2009, 03:25 AM
#1
Burning Brakes
Thread Starter
Looking for Opinions on Cam Upgrade, Pauter Rods, Big Valve Head
I'll be tearing into my engine again this winter, and trying to assess various options for further upgrading things. It's still a 2.5L, and I'll be making a decision on increasing displacement based on condition of cylinder bores. Motor itself is fairly stock, have a crankscraper, mildly ported head, Fidanza flywheel. Most of the significant mods that I've made are bolt-on. I'm looking for opinions on the following -
(1) For a 2.5L running an upgraded 50 trim T04E turbo and around 320rwhp at 16psi boost, what is the value in running a bigger cam - say a Web Cam or Vitesse cam. Does anyone have any real-world before and after comparison - ie. how is low end torque affected, what sort of improvements at top end, etc.? I'm also thinking of moving to Vitesse upgraded valve springs at the same time, as I'm always worried about valve float when I'm on the track.
(2) I'm thinking about installing a set of Pauter rods, even if I don't increase the displacement. I like the idea of reducing the rotating mass. I'm already running a Fidanza flywheel and love it. I have a KEP Stg1 aluminum pp sitting on the shelf that will also be going in. I'm wondering if anyone else has this combo, and can comment on driveability with all of these lightened components (easier to stall car from a stop light, car doesn't coast well on the hwy, etc.)
(3) I'm also thinking about possibly upgrading my head in similar fashion as Nize has done on his 2.7L MID sleeved motor. Big valves, porting, etc. Question is, do others running this combo notice a significant reduction in low end torque? Also, what is the biggest restriction in our motors, the head? Or would it make more sense to mod the i/c end tank first, and/or extrune hone the intake and install a bigger throttle body? Or is a better flowing head a good improvement all on it's own?
Thanks!
(1) For a 2.5L running an upgraded 50 trim T04E turbo and around 320rwhp at 16psi boost, what is the value in running a bigger cam - say a Web Cam or Vitesse cam. Does anyone have any real-world before and after comparison - ie. how is low end torque affected, what sort of improvements at top end, etc.? I'm also thinking of moving to Vitesse upgraded valve springs at the same time, as I'm always worried about valve float when I'm on the track.
(2) I'm thinking about installing a set of Pauter rods, even if I don't increase the displacement. I like the idea of reducing the rotating mass. I'm already running a Fidanza flywheel and love it. I have a KEP Stg1 aluminum pp sitting on the shelf that will also be going in. I'm wondering if anyone else has this combo, and can comment on driveability with all of these lightened components (easier to stall car from a stop light, car doesn't coast well on the hwy, etc.)
(3) I'm also thinking about possibly upgrading my head in similar fashion as Nize has done on his 2.7L MID sleeved motor. Big valves, porting, etc. Question is, do others running this combo notice a significant reduction in low end torque? Also, what is the biggest restriction in our motors, the head? Or would it make more sense to mod the i/c end tank first, and/or extrune hone the intake and install a bigger throttle body? Or is a better flowing head a good improvement all on it's own?
Thanks!
10-23-2009, 01:09 PM
#2
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On #2 I had a lightened stock flywheel, KEP Stg2, stock rods, Wossner pistons (much lighter than stock) and never had any driveability issues (did hill starts just fine, all that usual stuff, and I could easily get moving without using the gas pedal). IMHO any issues would come more from the Fidanza than lighter rods as far as getting moving from a stop.
Had meaning engine is being rebuilt again now, with Carillo rods
Had meaning engine is being rebuilt again now, with Carillo rods
10-23-2009, 02:19 PM
#3
Nordschleife Master
1) A good cam will definatly be a big improvement on your setup. Can't go wrong with a Milledge cam.
2) As long as you don't lighten the crank you won't risk any issues such as stalling. I'm running a Spec fw, lightweight Spec clutch, no balance shafts, balanced internals and have absolutely no issues with driveability.
3) Larger ports might hurt velocity which would hurt midrange and torque. IMHO there's a other, better ways, to spend money than a big valve head when on the hunt for more power.
2) As long as you don't lighten the crank you won't risk any issues such as stalling. I'm running a Spec fw, lightweight Spec clutch, no balance shafts, balanced internals and have absolutely no issues with driveability.
3) Larger ports might hurt velocity which would hurt midrange and torque. IMHO there's a other, better ways, to spend money than a big valve head when on the hunt for more power.
10-23-2009, 02:53 PM
#4
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Hi Ian,
Considering the turbo you are running and the boost/power levels, you may not see the full advantages of some of the items you are considering.
1a- The valve springs should be looked at as a maintenance item first then as a performance mod second. If your valve springs are worn out, then it's time to replace them. With the appropriate valve springs you don't have to worry about valve float at higher boost. When chosong a performance spring, you also need to worry about coil bind, which is related to the valve lift based on the cam. So if you need valve springs, upgrading to performance springs makes sense.
1b- Cams move your powerband around. Some are lumpy at idle, many do not address some of the inherited characteristics of the 951 (spoolup, back pressure,...). The more aggressive the cam is, the less streetable it will be. A cam that makes a ton of power up top, may not be the best cam for street driving. So cam selection can be a bit tricky. It's easy to see the performance gains on a dyno chart, but street manners are something you must experience to decide on what you can live with. If there are any emissions to deal with, it makes the selection even harder. So when deciding on a cam, focus your search on what is more important to you, street, track,... There is no one size fits all! In addition to the cams you expressed interest in, JME offers a good selection as well.
2. Aftermarket rods are not going to hurt drivability. There are many rods to chose from, Pauter, Carrillo, Wossner to name a few.... Most are in the same weight class till you jump to TI, which is extreme for a 951. The LWF will make some difference, however it's not a problem, you'll get used to it in no time.
3- A big valve head is nice to have. But with the turbo you have and the boost level/power you are running, you will not see the full benefits. A nicely modified head, where flow and velocity are both addressed will increase the Volumetric efficiency of your engine. Of course you will need a cam to compliment the head. At the power level you are dealing with, a good valve job (good seat work) and minor porting using a stock head might be more beneficial hp/$ wise.
A few more items that will help you make a educated decision and save you lots of headache and heartache.
- Talking to someone who actually used a product is a big plus.
- Investigate before you pay. There are plenty of questionable parts offered (talk about a head/cam that self destruct, or a engine that comes apart in a short period after initial run, or a replacement engine that sits at the builder's shop for a long time while the customer is waiting...). Make sure a 2 week turnaround does not turn into a year plus!!!
- When changing heads/cams make sure your your engine management can handle the new changes.
- Look at it as a system vs. a component.
Good luck.
Considering the turbo you are running and the boost/power levels, you may not see the full advantages of some of the items you are considering.
1a- The valve springs should be looked at as a maintenance item first then as a performance mod second. If your valve springs are worn out, then it's time to replace them. With the appropriate valve springs you don't have to worry about valve float at higher boost. When chosong a performance spring, you also need to worry about coil bind, which is related to the valve lift based on the cam. So if you need valve springs, upgrading to performance springs makes sense.
1b- Cams move your powerband around. Some are lumpy at idle, many do not address some of the inherited characteristics of the 951 (spoolup, back pressure,...). The more aggressive the cam is, the less streetable it will be. A cam that makes a ton of power up top, may not be the best cam for street driving. So cam selection can be a bit tricky. It's easy to see the performance gains on a dyno chart, but street manners are something you must experience to decide on what you can live with. If there are any emissions to deal with, it makes the selection even harder. So when deciding on a cam, focus your search on what is more important to you, street, track,... There is no one size fits all! In addition to the cams you expressed interest in, JME offers a good selection as well.
2. Aftermarket rods are not going to hurt drivability. There are many rods to chose from, Pauter, Carrillo, Wossner to name a few.... Most are in the same weight class till you jump to TI, which is extreme for a 951. The LWF will make some difference, however it's not a problem, you'll get used to it in no time.
3- A big valve head is nice to have. But with the turbo you have and the boost level/power you are running, you will not see the full benefits. A nicely modified head, where flow and velocity are both addressed will increase the Volumetric efficiency of your engine. Of course you will need a cam to compliment the head. At the power level you are dealing with, a good valve job (good seat work) and minor porting using a stock head might be more beneficial hp/$ wise.
A few more items that will help you make a educated decision and save you lots of headache and heartache.
- Talking to someone who actually used a product is a big plus.
- Investigate before you pay. There are plenty of questionable parts offered (talk about a head/cam that self destruct, or a engine that comes apart in a short period after initial run, or a replacement engine that sits at the builder's shop for a long time while the customer is waiting...). Make sure a 2 week turnaround does not turn into a year plus!!!
- When changing heads/cams make sure your your engine management can handle the new changes.
- Look at it as a system vs. a component.
Good luck.
10-23-2009, 03:17 PM
#5
Rennlist Member
I can comment on the cam issue;
Definitely an improvement in power, but really to get the most out of it, you have to see the whole thing as a package. Slapping in a cam all by itself might leave you disappointed.
Ideally, with a more aggressive cam on a turbo engine, the intake manifold pressure should be slightly more than the turbine inlet pressure so that the cam can do its work in filling the cylinders properly. Too much back pressure will cause serious exhaust reversion with the big cam which will take a big bite out of the power potential.
So, therefore you'll probably need a bigger exhaust housing than usual. So yes, the turbo will spool slower and together with a cam that moves maximum airflow up the RPM scale a bit, you'll be a little more sluggish at the lower RPMs.
You can make up for this by increasing displacement and/or increasing compression ratio (big cams love higher CR with less risk of detonation).
You will have to upgrade the valve springs. Stock, I believe is somewhere around 130 lbs seat pressure; you should have around 160 lbs.
So, depending on the aggressiveness of the cam, and your turbo configuration, you will experience more acceleration at any given boost level, and which tends to not fall off as much at the higher RPMs.
Because of the higher achievable RPMs, one could even argue that you could use shorter gearing, which enhances the acceleration even more, and renders the lower RPM sluggishness non-exsistant.
Like I said, you really have to treat it as a packaged engineering project.
Sorry, just noticed that Vitesse already touched on info regarding the cam topic
(it takes me forever to post)
Definitely an improvement in power, but really to get the most out of it, you have to see the whole thing as a package. Slapping in a cam all by itself might leave you disappointed.
Ideally, with a more aggressive cam on a turbo engine, the intake manifold pressure should be slightly more than the turbine inlet pressure so that the cam can do its work in filling the cylinders properly. Too much back pressure will cause serious exhaust reversion with the big cam which will take a big bite out of the power potential.
So, therefore you'll probably need a bigger exhaust housing than usual. So yes, the turbo will spool slower and together with a cam that moves maximum airflow up the RPM scale a bit, you'll be a little more sluggish at the lower RPMs.
You can make up for this by increasing displacement and/or increasing compression ratio (big cams love higher CR with less risk of detonation).
You will have to upgrade the valve springs. Stock, I believe is somewhere around 130 lbs seat pressure; you should have around 160 lbs.
So, depending on the aggressiveness of the cam, and your turbo configuration, you will experience more acceleration at any given boost level, and which tends to not fall off as much at the higher RPMs.
Because of the higher achievable RPMs, one could even argue that you could use shorter gearing, which enhances the acceleration even more, and renders the lower RPM sluggishness non-exsistant.
Like I said, you really have to treat it as a packaged engineering project.
Sorry, just noticed that Vitesse already touched on info regarding the cam topic
(it takes me forever to post)
