My car went on the dyno - 986 Forum - The Community for Porsche Boxster & Cayman Owners

Some of you may recall my 2003 S suffered and IMSB failure last July and I elected to have my engine rebuilt by my local independent Porsche shop. As part of that process I decided to have the engine enlarged from the stock 3.2 to a 3.6 using LN Nickies and JE Pistons. Other modifications in the rebuild were ARP rod bolts and the 987 oil pressure relief spring/valve and the IMS Solutions. External to the engine modifications included a 987 airbox, Fabspeed Sport headers with catalysts and a Softronic custom tune for the 3.2 increased to 3.6 and a 987 MAF. The car ran and performed nice after I got it back and the engine was broken in. But my shop suggested that the tune could be verified and perhaps improved with some dyno pulls, so I scheduled an appointment which was yesterday. I was able to see one demonstration of my car on the dyno. I was expecting to see a typical rolling road with the rear tires on drums, but the shop uses a Dynapack unit which has hydraulic resistance/measurement units that attaches directly to the hub of each driven wheel after the wheel is removed. When they do a run on this kind of dyno they just put it in 4th gear and run it up through the rpm range. The initial pull showed my car had 243.7 HP at the wheels, and that it was running rich. They were able to get Softronic to modify the tune file and it ran better but they could tell it was still being restricted by the exhaust, which was stock after the headers. They had in stock a new set of Circuit Werks mid pipes with resonators but no secondary cats, so I gave them the go ahead to install them which increased the HP to 254.7. The shop said the HP at the wheels is about 85% of the HP at the flywheel, so that would be just about 300 HP at the flywheel. You can see the before (green) and after (red) in the picture below. I am happy with the results. On the highway the car pulls very nicely when at 3,000 RPM in 6th gear. It is even more awesome running up through the gears and really starts to come alive after 4,000 RPM. The sound is a bit louder with the 987 airbox, headers and midpipes but not annoying and there is no drone with the stock muffler. And I'm still learning to drive on the track in HPDE's, where I need more power like a turtle needs air brakes, so it's all good!

Very nice, thought it would be a bit higher, but I have heard those types of dyno machines usually show a lower number then the normal type dyno machines. I think you meant "before (green) and after (red) in the picture below."

Quotes source post: 595140

Thanks, yes I did mean that. I will edit the original post.

weird, my 3.2 with headers/987 airbox, 3.4 throttle body, softronic tune, and full exhaust put down 254rwhp on powertech's dyno. I'd expect a 3.6 to do better.

Quotes source post: 595164

Those are great numbers you have. The throttle body, intake plenum and manifold on mine are still stock, as are the cams and I assume the compression ratio is stock or close to stock too. My headers have the cats so they are still a little restricted vs the catless race headers. Mike told me he hasn't seen much in HP gains with bigger throttle bodies and IPD plenums and in some cases he has seen HP decreases. Keith said he's seen an increase on his Boxster S with a larger throttle body and plenum but his is a race car with open exhaust and lots of internal engine modifications. They did 7 dyno pulls and everything was done in one day. The rebuilt engine only has a little over 2,000 miles on it and is still burning a little bit of oil which should stop soon. Maybe when the rings are fully seated it will make a little more, but I don't think I'll be investing in more dyno time to find out .

Sounds good Paul. And you have that nice feeling that your engine shouldn’t blow up any time soon! Im looking forward to dynoing mine when it gets broken in. At this point I have the 987 airbox and maf with the larger TB and tuning like Quadcammer. Chinese headers and circuitwerks high flow cats and stock muffler. Hope it performs nicely!

For everything done to it I would have expected a higher number. I'm thinking maybe your intake and exhaust systems might be holding the motor back. I'm a firm believer that the 986 intake and exhaust systems are big corks. Maybe a 996 intake and larger TB will help those HP numbers. Your stock muffler and U pipes are tiny. They can't be helping the situation either. I have a thread about my dyno run that might help. http://986forum.com/forums/performance-technical-chat/71568-two-modified-boxsters-dyno-2.html

Thanks guys I appreciate the tips but am going to stay put for now on the engine, intake and exhaust. In addition to the cost of the rebuilt engine I also put a new battery in and just ordered a set of 18 inch Michelin Pilot Sport 4S tires. The intake and exhaust mods are deeper than I am willing to do myself and I’m still a novice on the track (which I may remain doing only 3 or 4 events per year and being 62). Since I decided to have my engine rebuilt I did the LN Nickies, 987 airbox and tune, but I drew the line at ARP rod bolts and retained the stock rods. But in a year or two we’ll see if I get the bug for more power!