World's first FI low compression E92 stroker motor build
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From: Morgan Hill, CA
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World's first FI low compression E92 stroker motor build
PencilGeek low compression motor rebuild with pictures
Background on Low Compression
As many people know, I'm not fond of high compression and forced induction. In my opinion, if you want any serious performance, the two just don't go together. When I decided to supercharge the RD Sport RS-46 stroker motor, I always held out the possibility that I might want to lower the compression ratio. There's basically two ways to do this: 1) Low compression pistons, and 2) Thicker head gasket.
I've never liked the thicker head gasket approach because it alters the valve timing. A good tuner on a double-VANOS cylinder head like those found on the S65 "might" be able to fix it. But in my opinion, this is not the correct approach because it reduces the variability of the cam timing. For example, let's say the original VANOS allowed for +/- 5 degrees (I'm not sure the exact number, but I think it's in this ball park). When you add a thicker head gasket, the cam's natural position is rotated further to one side because of the extra distance between the crank sprocket and cam sprocket. So let's say this alters the cam timing -1 degree. This would mean the VANOS programming (if left unchanged) would no longer be +/- 5 degrees, but would be -6 to +4 degrees. To fix this correctly, the VANOS literally dozens (if not scores) of VANOS maps in the ECU would need to be altered to fix this. I'm sorry, but I'd prefer not to go this approach. So if I ever wanted to lower my compression ratio, that meant I would need to get low compression pistons.
The history of my decision
When I dropped off my car at ESS to get the SC installed, I met with AJ for a couple of hours. Sometime during the discussion, I asked about lowering the compression ratio. My original idea was to run the Mojave Mile, Texas Mile, then decide what I wanted to do. I knew from my CarTest simulations that I would need about 700whp to hit 200MPH in the standing mile. And I also knew that I was nowhere near that number. So almost immediately, I was on the phone with RD Sport asking about low compression pistons.
On February 22nd, I send an email to RD Sport, asking about the piston design. I had already given Federico instructions to "investigate" the low compression piston design. We had very good information that Mahle already a forced induction piston design that could be directly adapted to the S65 motor. So I gave Federico the instruction to investigate this piston and get back to me.
In the mean time, we ran the Mojave Mile and Texas Mile. During this time, Federico of RD Sport confirmed that Mahle does have a forced induction piston that can be directly adapted to the S65 motor. Needless to say, that's EXACTLY what I wanted to hear.
In parallel with this investigation with Mahle, I did my own investigations with sleeving the block. I knew "tightie's" motor was sleeved and CP pistons used, so I also investigated this approach as well. Zolti at Auto Talent was NOT a fan of sleeving the block, but ESS was. In fact, my impression was that Zolti was very much against the idea. It really concerned me that the guy who assembled tightie's bottom end and saw it first hand was not in favor of the idea for my own motor. And then, the other shoe dropped. The machine shop who would be sleeving the block refused to do it. This is NOT the machine shop who sleeved tightie's motor, but this IS the machine shop who has seen 7-8 of these blocks already and machined them for stroker motors. So the way I figured it, if this machine shop has seen 7-8 of these blocks already, and refuses to do the work because they say it will weaken the block too much -- this is not what I wanted to hear if I was going to consider this approach. Luckily, we had our Mahle piston options -- so if I DID decide to lower the compression ratio, I only had one choice.
I believe it was sometime after the Texas Mile and before M-Fest that I finally decided to lower the compression ratio. All I remember was sitting in a restaurant in Valencia, CA eating breakfast when I called Federico and gave him the green light to order the pistons. Since I live 300 miles away from Valencia, that means the most likely date for my decision was the week before M-Fest 2010. So the most likely date for my decision was April 15th, 2010.
The wait, and the setbacks
The plan was to wait for the pistons to be made, then drive the car down to Auto Talent and pull the motor and rebuild it. So a few days before the pistons were supposed to arrive, I drove the car down to Auto Talent. Then the waiting started: the pistons didn't arrive on time. So I kept calling, and calling, and it seemed to me as if nobody wanted to give me "the bad news." Since I had been unable to get in touch with Federico, I called Sam instead (knowing that they talk on a regular basis). I asked Sam point blank about the pistons: "WHERE ARE THEY?" You know it's not going to be a good conversation when the answer begins "I shouldn't be the one to tell you this..."
So at that point, I knew something was wrong with the pistons. I sent Federico a text message, telling that I knew there was some type of screw up...and to just let me know what it is. That's when I got the bad news. Mahle had shipped regular high compression pistons -- not the low compression, forced induction pistons with special rings on them. Mahle agreed to eat the pistons (of course), but it would be another 4-week delay until they arrived.
Two weeks ago, the new pistons arrived. I decided to take a stroll down to SoCal for the Labor Day weekend and photograph the pistons, and take more pictures of the older pistons and connecting rods -- since I was now planning to put these pistons up for sale to anybody who wants to build a stroker motor for cheap.
Just when you think the drama and delays were over, there was some more disappointing news. Just to be sure that the connecting rods were up to the extra power, RD Sport contacted the manufacturer and asked them. They immediately vetoed the idea of using the NA connecting rods for my new FI application. I don't think they were even thrilled that we used the other rods for the SC stroker in the first place. So Federico gave me the choice: I can continue to use my existing connecting rods, or we can wait another 4 weeks for a new design and new set of connecting rods. Being a perfectionist, the choice was a no-brainer. We gave the new motor specs for boost and power estimates, and gave the green light for a new set of connecting rods. So with these new rods on order, I now have a full set of 8 pistons and 8 connecting rods for sale to anybody who wants to build a less expensive stroker motor. PM me for info.
Background on Low Compression
As many people know, I'm not fond of high compression and forced induction. In my opinion, if you want any serious performance, the two just don't go together. When I decided to supercharge the RD Sport RS-46 stroker motor, I always held out the possibility that I might want to lower the compression ratio. There's basically two ways to do this: 1) Low compression pistons, and 2) Thicker head gasket.
I've never liked the thicker head gasket approach because it alters the valve timing. A good tuner on a double-VANOS cylinder head like those found on the S65 "might" be able to fix it. But in my opinion, this is not the correct approach because it reduces the variability of the cam timing. For example, let's say the original VANOS allowed for +/- 5 degrees (I'm not sure the exact number, but I think it's in this ball park). When you add a thicker head gasket, the cam's natural position is rotated further to one side because of the extra distance between the crank sprocket and cam sprocket. So let's say this alters the cam timing -1 degree. This would mean the VANOS programming (if left unchanged) would no longer be +/- 5 degrees, but would be -6 to +4 degrees. To fix this correctly, the VANOS literally dozens (if not scores) of VANOS maps in the ECU would need to be altered to fix this. I'm sorry, but I'd prefer not to go this approach. So if I ever wanted to lower my compression ratio, that meant I would need to get low compression pistons.
The history of my decision
When I dropped off my car at ESS to get the SC installed, I met with AJ for a couple of hours. Sometime during the discussion, I asked about lowering the compression ratio. My original idea was to run the Mojave Mile, Texas Mile, then decide what I wanted to do. I knew from my CarTest simulations that I would need about 700whp to hit 200MPH in the standing mile. And I also knew that I was nowhere near that number. So almost immediately, I was on the phone with RD Sport asking about low compression pistons.
On February 22nd, I send an email to RD Sport, asking about the piston design. I had already given Federico instructions to "investigate" the low compression piston design. We had very good information that Mahle already a forced induction piston design that could be directly adapted to the S65 motor. So I gave Federico the instruction to investigate this piston and get back to me.
In the mean time, we ran the Mojave Mile and Texas Mile. During this time, Federico of RD Sport confirmed that Mahle does have a forced induction piston that can be directly adapted to the S65 motor. Needless to say, that's EXACTLY what I wanted to hear.
In parallel with this investigation with Mahle, I did my own investigations with sleeving the block. I knew "tightie's" motor was sleeved and CP pistons used, so I also investigated this approach as well. Zolti at Auto Talent was NOT a fan of sleeving the block, but ESS was. In fact, my impression was that Zolti was very much against the idea. It really concerned me that the guy who assembled tightie's bottom end and saw it first hand was not in favor of the idea for my own motor. And then, the other shoe dropped. The machine shop who would be sleeving the block refused to do it. This is NOT the machine shop who sleeved tightie's motor, but this IS the machine shop who has seen 7-8 of these blocks already and machined them for stroker motors. So the way I figured it, if this machine shop has seen 7-8 of these blocks already, and refuses to do the work because they say it will weaken the block too much -- this is not what I wanted to hear if I was going to consider this approach. Luckily, we had our Mahle piston options -- so if I DID decide to lower the compression ratio, I only had one choice.
I believe it was sometime after the Texas Mile and before M-Fest that I finally decided to lower the compression ratio. All I remember was sitting in a restaurant in Valencia, CA eating breakfast when I called Federico and gave him the green light to order the pistons. Since I live 300 miles away from Valencia, that means the most likely date for my decision was the week before M-Fest 2010. So the most likely date for my decision was April 15th, 2010.
The wait, and the setbacks
The plan was to wait for the pistons to be made, then drive the car down to Auto Talent and pull the motor and rebuild it. So a few days before the pistons were supposed to arrive, I drove the car down to Auto Talent. Then the waiting started: the pistons didn't arrive on time. So I kept calling, and calling, and it seemed to me as if nobody wanted to give me "the bad news." Since I had been unable to get in touch with Federico, I called Sam instead (knowing that they talk on a regular basis). I asked Sam point blank about the pistons: "WHERE ARE THEY?" You know it's not going to be a good conversation when the answer begins "I shouldn't be the one to tell you this..."
So at that point, I knew something was wrong with the pistons. I sent Federico a text message, telling that I knew there was some type of screw up...and to just let me know what it is. That's when I got the bad news. Mahle had shipped regular high compression pistons -- not the low compression, forced induction pistons with special rings on them. Mahle agreed to eat the pistons (of course), but it would be another 4-week delay until they arrived.
Two weeks ago, the new pistons arrived. I decided to take a stroll down to SoCal for the Labor Day weekend and photograph the pistons, and take more pictures of the older pistons and connecting rods -- since I was now planning to put these pistons up for sale to anybody who wants to build a stroker motor for cheap.
Just when you think the drama and delays were over, there was some more disappointing news. Just to be sure that the connecting rods were up to the extra power, RD Sport contacted the manufacturer and asked them. They immediately vetoed the idea of using the NA connecting rods for my new FI application. I don't think they were even thrilled that we used the other rods for the SC stroker in the first place. So Federico gave me the choice: I can continue to use my existing connecting rods, or we can wait another 4 weeks for a new design and new set of connecting rods. Being a perfectionist, the choice was a no-brainer. We gave the new motor specs for boost and power estimates, and gave the green light for a new set of connecting rods. So with these new rods on order, I now have a full set of 8 pistons and 8 connecting rods for sale to anybody who wants to build a less expensive stroker motor. PM me for info.
Last edited by Divexxtreme; Sep 19, 2010 at 05:26 PM. Reason: active link to another forum
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Whose rods are they?
Sounds like a cool project, but remember, you're thread title says it all.
It's easy to get frustrated with setbacks, dilemmas, etc. But when you're doing something first, there will almost always be hurdles to overcome.
Sounds like you're on the right track, do it right the first time.
Sounds like a cool project, but remember, you're thread title says it all.
It's easy to get frustrated with setbacks, dilemmas, etc. But when you're doing something first, there will almost always be hurdles to overcome.
Sounds like you're on the right track, do it right the first time.
Thread Starter
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Registered User
Joined: Nov 2009
Posts: 95
From: Morgan Hill, CA
Rep Power: 22
Both the stroker motor and new motor will use Pankl rods. 
I worked in a race engine shop in my youth. The rule of thumb is to take whatever estimate the engine builder gives you...and double it. I'm in no hurry. In the mean time, I'm accumulating carbon credits driving my Prius...and I'll need those credits once the project is finished.
Once the new connecting rods are delivered, I'll be posting pictures of both sets side-by-side. That way everybody will see the difference.
Sounds like a cool project, but remember, you're thread title says it all.
It's easy to get frustrated with setbacks, dilemmas, etc. But when you're doing something first, there will almost always be hurdles to overcome.
Sounds like you're on the right track, do it right the first time.
It's easy to get frustrated with setbacks, dilemmas, etc. But when you're doing something first, there will almost always be hurdles to overcome.
Sounds like you're on the right track, do it right the first time.
Once the new connecting rods are delivered, I'll be posting pictures of both sets side-by-side. That way everybody will see the difference.
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From: Morgan Hill, CA
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Somehow, I've managed to put 30,000 miles on the car -- even though it's been a perpetual project car.
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High EGT's were killing O2 sensors. However at the Texas Mile we also ran Q16 leaded gas -- which definitely helped kill one set of O2's.
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I finally figured out a way to post my own pictures without another forum attached, and without uploading to a 3rd party photo site. So I started my own photo album site, not associated with any forums. This way nobody can fight over water marks, or forum links, etc.
Many people have been asking questions about my new motor build and wanting to find pictures. So I just started my own photo server for my own pictures. That should solve the problem -- no forums involved and everybody can enjoy the pictures without forum admins/mods fighting over links and watermarks.
Main site:
http://www.rcollins-home.org/photobucket
Here's some highlights:
Pre stroker tear down:
http://www.rcollins-home.org/photobu...s.php?album=10
Stroker motor build:
http://www.rcollins-home.org/photobu...s.php?album=11
Mojave Mile:
http://www.rcollins-home.org/photobu...s.php?album=60
Motor tear down for new low compression build:
http://www.rcollins-home.org/photobu...s.php?album=62
http://www.rcollins-home.org/photobu...s.php?album=81
http://www.rcollins-home.org/photobu...s.php?album=82
http://www.rcollins-home.org/photobu...s.php?album=85
http://www.rcollins-home.org/photobu...s.php?album=88
Many people have been asking questions about my new motor build and wanting to find pictures. So I just started my own photo server for my own pictures. That should solve the problem -- no forums involved and everybody can enjoy the pictures without forum admins/mods fighting over links and watermarks.
Main site:
http://www.rcollins-home.org/photobucket
Here's some highlights:
Pre stroker tear down:
http://www.rcollins-home.org/photobu...s.php?album=10
Stroker motor build:
http://www.rcollins-home.org/photobu...s.php?album=11
Mojave Mile:
http://www.rcollins-home.org/photobu...s.php?album=60
Motor tear down for new low compression build:
http://www.rcollins-home.org/photobu...s.php?album=62
http://www.rcollins-home.org/photobu...s.php?album=81
http://www.rcollins-home.org/photobu...s.php?album=82
http://www.rcollins-home.org/photobu...s.php?album=85
http://www.rcollins-home.org/photobu...s.php?album=88
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