Spec Boxster Build

[seningen]

Originally Posted by thstone

OK, let's talk horsepower.

At the AutoClub Speedway race, the POC had a dyno to measure power output at the rear wheels (there is currently no maximum power spec). The top 3 qualifiers and top 3 race finishers were required to have their cars tested. I had mine tested of my own desire.

Here are three data points;

My Car: 196hp
Car 2: 187hp
Car 3: 203hp

From my perspective, its good news that my $1,800 salvage yard, never been opened, previous tiptronic, engine with 90,000 prior miles still managed 196hp at the rear wheels!

Of course, you might be wondering: with a rating of 200hp at the crank, how can I get 194hp at the rear wheels from a stock engine?

200hp at the crank
- 20hp 10% driveline loss
+ 7hp TopSpeed cat back exhaust (verified on dyno: Spec Boxster Build)
+ 5hp Removal of cat's (verified on dyno)
+ 5hp Under drive pulley (per other testing)
________
196 hp net at the rear wheels

Nice plug for the junk yard :-)

What is allowed in an engine rebuild? Can you custom make the rings?
What limits are there on the valve job.

IMS retrofit isn't going to get you anything.

Anything else would seem to be illegal.

What weight oil do you guys run?

Could you alter the cam to exhaust timing on the vario-cam by displacing a tooth and still not have interference but gain anything?

Note I don't race spec boxster -- but I've been involved in a few M96 rebuilds and its not hard to accidentally alter the vari-cam timing during install (but I've always caught it :-).

Mike

[Eric523]

Originally Posted by seningen

Nice plug for the junk yard :-)

What is allowed in an engine rebuild? Can you custom make the rings?
What limits are there on the valve job.

IMS retrofit isn't going to get you anything.

Anything else would seem to be illegal.

What weight oil do you guys run?

Could you alter the cam to exhaust timing on the vario-cam by displacing a tooth and still not have interference but gain anything?

Note I don't race spec boxster -- but I've been involved in a few M96 rebuilds and its not hard to accidentally alter the vari-cam timing during install (but I've always caught it :-).

Mike

Yeah, some of the high mile motors run good after being loosened up!

There aren't very clear/good/complete rules when it comes to the rebuilds like you would find in Spec Miata or a class run by a more professional organization, unfortunately. So the term "stock spec" really covers most of your questions. At the least, we're trying to make sure everyone is using stock components.

We're supposed to be using stock Porsche pistons and rings. No aftermarket pistons/rings built to same size or anything like that. I have not seen limitations on valve jobs, other than the valves need to be stock.

Oil weight is up to the competitor/engine builder, there is no stock spec. I use 0w-50 Mobil 1 Racing oil.

You cannot legally alter the cam timing. However, I'm sure there are some that do. It is not something I've done or experimented with so I can't speak to the specific advantages.

[Eric523]

Originally Posted by Eric523

There aren't very clear/good/complete rules when it comes to the rebuilds like you would find in Spec Miata or a class run by a more professional organization, unfortunately. So the term "stock spec" really covers most of your questions. At the least, we're trying to make sure everyone is using stock components.

We're supposed to be using stock Porsche pistons and rings. No aftermarket pistons/rings built to same size or anything like that. I have not seen limitations on valve jobs, other than the valves need to be stock.

It has come to my attention that my statement above has been cherry picked to support ones own personal thoughts and I just want to clarify...
A gentleman asked specifically about valve job rules and I replied above, that there are no specific rules in the rule book other than ''stock'', unfortunately. Some that wish to read into that assume that meant I would manipulate a valve job... that's not the case, just you hearing what you want to hear. It was a reply to a question specifically about valve job specifications.
As referenced just beforehand, a rule set like spec Miata actually has several pages about engine internal specifics, like posted below.
I did not say ''I have not seen limitations'' because I have exploited them, I said that because there are no posted values of limitations...

Short of buying new cylinder heads for every rebuild, there are modifications that need to be completed on any regular standard engine build. This is supposed to be cost controlled spec racing and engine rebuilding is part of it. There should be rules with values about plunge cutting and valve jobs and decking heads like any other reasonable spec but BSR is not at that level of precision, yet.

People will believe what they want... even with several independent dyno runs at several tracks back to back against other cars right out of qualifying. We know what the cars are running HP wise across the field because they have ramped up dyno testing and that is a big step forward.

[seningen]

Originally Posted by Eric523

It has come to my attention that my statement above has been cherry picked to support ones own personal thoughts and I just want to clarify...
A gentleman asked specifically about valve job rules and I replied above, that there are no specific rules in the rule book other than ''stock'', unfortunately. Some that wish to read into that assume that meant I would manipulate a valve job... that's not the case, just you hearing what you want to hear. It was a reply to a question specifically about valve job specifications.
As referenced just beforehand, a rule set like spec Miata actually has several pages about engine internal specifics, like posted below.
I did not say ''I have not seen limitations'' because I have exploited them, I said that because there are no posted values of limitations...

Short of buying new cylinder heads for every rebuild, there are modifications that need to be completed on any regular standard engine build. This is supposed to be cost controlled spec racing and engine rebuilding is part of it. There should be rules with values about plunge cutting and valve jobs and decking heads like any other reasonable spec but BSR is not at that level of precision, yet.

People will believe what they want... even with several independent dyno runs at several tracks back to back against other cars right out of qualifying. We know what the cars are running HP wise across the field because they have ramped up dyno testing and that is a big step forward.

Eric,

Never thought otherwise -- basically having a beer discussion over the net :-)

I'm building a pair of SP-1s, so arguably my question is mute to me. However I do track a Boxster S and I have either rebuilt or been a part of about a dozen rebuilds of these engines and I was trying to envision how the HPs could vary.

Note I'm a EE and shade tree mechanic hack not a professional engine builder -- so this is more of a thought exercise for me.

Mike

[Eric523]

Originally Posted by seningen

Eric,

Never thought otherwise -- basically having a beer discussion over the net :-)

I'm building a pair of SP-1s, so arguably my question is mute to me. However I do track a Boxster S and I have either rebuilt or been a part of about a dozen rebuilds of these engines and I was trying to envision how the HPs could vary.

Note I'm a EE and shade tree mechanic hack not a professional engine builder -- so this is more of a thought exercise for me.

Mike

Thanks, I wasn't referring to you at all. It's a good question and anyone that has built an engine would know that cylinder head servicing is part of it. You can't rebuild a head to exact stock originally delivered specs and still successfully service it. Replacing cylinder heads with new every time adds another $8k to an engine rebuild and a terrible idea for cost controlled spec racing. Porsche dealership service departments and factory re manufactured engine program all service heads in similar ways within certain tolerances. Even if you ordered a rebuilt crate 2.5L engine from Porsche, the cylinder head has been serviced. Order up a rebuilt cylinder head from Porsche and that has also been serviced. Unfortunately, those tolerances are not really public info or written in our rule books so there is no guidance as to what acceptable "stock" range actually is. So when I said, "I have not seen limitations", that's what I meant. Not "there are none so it's wide open for porting and polishing and ceramic coatings and flow bench testing." As you can see, some spec classes do have a handle on such things, and Boxster Spec is not one of them.

[seningen]

Originally Posted by Eric523

Yeah, some of the high mile motors run good after being loosened up!

There aren't very clear/good/complete rules when it comes to the rebuilds like you would find in Spec Miata or a class run by a more professional organization, unfortunately. So the term "stock spec" really covers most of your questions. At the least, we're trying to make sure everyone is using stock components.

We're supposed to be using stock Porsche pistons and rings. No aftermarket pistons/rings built to same size or anything like that. I have not seen limitations on valve jobs, other than the valves need to be stock.

Oil weight is up to the competitor/engine builder, there is no stock spec. I use 0w-50 Mobil 1 Racing oil.

You cannot legally alter the cam timing. However, I'm sure there are some that do. It is not something I've done or experimented with so I can't speak to the specific advantages.

I was reading up on the VarioCam -- as I understand it, the solenoid opens up from about 3K-5K, and is shut off above and below. If it wasn't working "properly", you would have different engine behavior. I'm not sure if that would be better or worse overall. I have to think there would be a tradeoff if it was to be engaged all the time as an example.

Mike

[Eric523]

Originally Posted by seningen

I was reading up on the VarioCam -- as I understand it, the solenoid opens up from about 3K-5K, and is shut off above and below. If it wasn't working "properly", you would have different engine behavior. I'm not sure if that would be better or worse overall. I have to think there would be a tradeoff if it was to be engaged all the time as an example.

Mike

Better to be working as designed, for sure. These solenoids and tensioners fail from time to time and there is an overall performance loss.