Boxster S M96/21 overbore to 3.6/3.8 with stock DME?
 

I have a 2002 Boxster S 3.2

Lost power in an autocross run, turns out the engine is now a rebuildable core (cracked head or d chunk, tear down pending, still ran, no expensive noises but all the coolant ended up in the crankcase)

Planning to have LN engineering bore the case halves to 3.6 or 3.8 and rebuild. I realize a used engine would be cheaper, but I really like doing engine work, especially with high performance parts.

My question is as follows:

Is it safe to run a 3.6 or 3.8 M96/21 with the stock Boxster S DME?

I don’t want to run my expensive new engine lean and fry it. I don’t care that much if the stock tune isn’t optimal, worried more if it is safe to run like that. I am sure I will eventually upgrade the tune, but would like to run with the stock tune until I can get to a shop with the skills to do it right.

Follow up question:

who has the skills to tune my DME?

I don’t want to swap to a newer DME if avoidable, would rather have my current one flashed. If I have to do it now to make it safe I will, but would prefer to wait if I can.

Leaning toward the 3.8 for the extra torque, I realize the 3.2 heads really don’t flow enough for that displacement, but that actually enhances low end torque, which would be great for autocross! if there is a compelling reason to go 3.6 I’d love to hear it.

Thanks for any assistance you can offer!

Silber

[QUOTE=Silber;628427] Planning to have LN engineering bore the case halves to 3.6 or 3.8 and rebuild. Is it safe to run a 3.6 or 3.8 M96/21 with the stock Boxster S DME?


Perhaps Charles at LN would be a right person to ask this question as he has plenty of experience building increase bored engines.. and he is a cool guy as well
.

I think I read you need the DME changed for the new engine specs.

My understanding is that swapping to a 2003+ engine the DME has to be changed as the Variocam system is entirely different.

Sticking with the stock engine but boring it larger should in theory be able to use the same 2002 DME.

My thought is I should be OK, my final engine will probably make about 320 hp and I think that could probably be supported by a stock DME. I am just hoping to get someone that’s an expert to tell me what’s what.

I had asked LN engineering sales people about the DME question but did not really get a full answer, I will call back as Gilles suggested.

Silber

My 2003 S was rebuilt as a 3.6 with LN Nickies. I have a custom Softronic tune made for the 3.2 bored to 3.6. After engine break-in, the car was run on a chassis dyno, the results were sent to Softronic and they made some further adjustments to it. My recollection is my shop said I could stay with the stock tune, but I elected to get the Softronic tune. I stayed with the stock throttle body and intake plenum, and my headers are a more restrictive since they have catalysts. If you're going to have move open headers, a 987 airbox and MAF, bigger throttle body and matching intake plenum, you'll probably want the custom tune.

Thanks for sharing your experience! Great to hear that Softronic will work with custom builds on their tunes. I have sent inquiries to a number of tuners, will see what they say.

Have a few mods that would influence a tune:
Cone intake
Headers w/o cats
High flow cats in rear position
Free flow muffler

Considering bigger MAF and throttle body, but since I’m using stock 5 chain 3.2 heads not sure how much gains to be had there...

Silber

I have a 2001 3.2 with LN 3.6 cylinders & JE pistons & lightly ported heads It will run just as good as the 3.6 in my car without touching the DME. Its for sale in the classified column.

http://986forum.com/forums/uploads02...1609609265.jpg

FWIW my shop recommended against the IPD Plenum and 74mm throttle body-they said they haven't seen power increases on stock engines and in some cases have seen power decreases on their dyno. I have also read comments that a larger throttle body is like putting a bigger faucet on a pipe. You get more flow opening the faucet just a little bit (part throttle), but opening up the faucet all the way (full throttle) doesn't add anything, because the pipe diameter is the limiting factor. I don't know the real answer, but I already spent more than enough so I opted not to change my throttle body or plenum. If I ever get to the point on the track where I'm using all the power I already have and need more from this car, I'll think about it.

Thanks for the offer, you are asking a very reasonable price. However, I’m leaning toward a 3.8 and have already started buying parts to build the engine myself. I enjoy engine work and am looking forward to the task as well.

Regards,

Silber

Good news! Softronic offers a tune for the 3.8 five chain overbore, just under $1,000 including cable.

With their reputation combined with the reasonable price this will be my choice for a flash. I am now pretty convinced that is safe to run the 3.8 with the stock DME, But more power is always better if you can swing it!

Thinking I will get the car running with the 3.8 with the stock DME and then do the flash later. Not 100% sure, but plan to do at least one dyno run. Probably after the flash, but one before and one after would be interesting too. I have asked Softronic if they think a dyno run with stock software is safe from over lean condition, will report what they say.

Silber

Softronic recommended that the flash be applied first. They said timing and fueling torque limiters would be off enough that it could cause a problem.

Additionally they recommended against chassis dyno in general, stating they were risky for a car.

Regards,

Silber

A chassis dyno is the only way to know/monitor how the engine is performing . Every car performs differently so a " fits all canned tune " may run lean on some and rich on another . If a chassis dyno is " risky for the car " does that mean on the street you are NEVER going to run the car up to redline ? I would be a little concerned about a software company selling a tune making certain claims about that tune but are hesitant or recommend you not verify the results . I have probably watched 50 + chassis dyno pulls on Porsche cars and am always amazed on the differences that need to be " tuned " .

Not trying to scare you or be a douche , just my thoughts . I wish you the best on your rebuild and hope all goes as planned . Have fun ........ take your time and enjoy . :cheers:

Thanks for the words of encouragement!! I have a feeling its going to be quite a process.

I know Softronic is very well respected, perhaps i mis-read their advice, or there is some other way they can verify the tune, perhaps by a dump from the DME?

regards,

Silber

The shop that works on my car and rebuilt my engine and they work with Softronic a lot. Softronic provided a custom tune for my 3.2 bored out to 3.6. After the engine was broken in, it went on the shop's Dynapack dyno, they sent results to Softronic and Softronic sent them back an updated tune the same day. I think they send the air fuel ratio results chart from the dyno runs to Softronic and then Softronic makes adjustments. If a chassis dynomometer isn't used, the engine would have to be out of the car and installed on an engine stand dynomometer.

Yeah, I guess the only other possible option would be a logging wideband O2 and some 1st and 2nd gear pulls on a suitable road or track?

Sounds like I must have misunderstood what he was saying.

regards,

Silber

Keep in mind the object of the game is to see how much they can lean out the Air/fuel mixture without causing engine damage!

Starting on the tear-down by pulling the plugs, and its looking like #2 ran lean till it fried. Would guess a partially plugged injector.

Plug is stuck in the head, cannot get it to come out.
Coil plug boot was partially stuck/melted to the plug.

The engine still ran, so hopefully no damage that makes the core non-rebuildable. Have a lot going on now so may not get the engine pulled and apart till spring. Thinking this rebuild may take a while due to life interfering with fun.

regards,

Silber

If you are going to send your engine case to LN for 3.8 Nickies and you have some type of schedule you want to adhere to, I would suggest tearing down the engine and sending the case to them as soon as you can. My case was sent to them late July/early August 2018 and came back to my shop late January/early February 2019. At that time they were quoting an 8 week turnaround. Once the Nickies are installed, they have to send the case to a specialized plater for the Nikasil plating on the bores, and there are only a limited number of platers who do this and they all have a big backlog. So it's not really their fault, but it does take time. If you don't have a schedule. just be prepared to wait and be happy if it's done sooner.