Geoffrey

Today I had hoped to be at Watkins Glen testing my car. Right now I'd be unloading my car into my garage, unpacking my tools and looking out over Seneca Lake as the sun comes up...but it's not to be. So what's the second best thing? being on the dyno. My engine now has two full heat cycles on the engine and with the exception of a small oil leak from an original hose that needs to be replaced, everything looks great and sounds great. The car was so loud with open pipes I couldn't really hear the engine so I installed a muffler system which keeps the car below Lime Rock's 89db sound level and I'll first dyno the car in this configuration. On the dyno that I'm using a 2001 GT3 Cup car will produce between 335-338rwhp. I am hoping that this engine will produce 325rwhp with the mufflers, we'll see. It has been my experience that the mufflers take away 20-25hp on similar 3.8l racing engines. In a few weeks I'll have another chance to dyno tune the car without mufflers and I'm hoping to be in the 345rwhp range. The most I've seen from a 3.8l engine on this dyno is 354 from a 13:1 compression engine running on racing fuel. My engine differs from Colin's engine in 3 fairly significant ways; I have about 1.5:1 less compression which will result in about 8hp less, although his piston design is far superior than the Mahles I'm running. His engine is 103mm where mine is 102 which should not be a significant factor. His pistons are designed to use a longer rod which increases piston speed which generally helps torque among other things.

I am going to bring my video camera and if there is time I'll capture some video and post it over the weekend. I'm migrating my website from one service provider to another on Saturday so it may not be up again until Sunday night.

Geoffrey

Chris M.

Video would be great. Hope it all goes well.

c

Geoffrey

Ok, sorry for the delays here. After some initial issues sorting out and syncing the throttle bodies as well as some other issues which took some time to resolve, I was back on the dyno today and finished the initial mapping of the engine. This is just the beginning and there is more work to be done but I'll run the engine this way initially. I am running with 93 octane Mobile gasoline and have the timing set slightly lower than max torque since I want to ensure everything is right before I set the engine on the edge. The datalogging shows a 32.7 degrees C (90F) intake air temp. I spent about 2 hours on the dyno mapping the car today.

As mentioned above, my goal was to produce 325rwhp with the mufflers, and my first swept run test after doing the steady state fuel and ignition timing resulted in 326rwhp - goal met! After some fine tuning I was able to produce 330rwhp and below is the graph. However, you'll notice a significant drop in torque around 4250 which I believe is a result of the headers that are on the car. I've seen this before with this same brand of headers and I still have the Champion developed racing headers with center outlet, but the car is just too noisy without any mufflers. I just couldn't bring myself to cut the headers yet so mufflers can be fabricated and I'll have to think on this over the winter. I have also seen about a 20rwhp drop due to the mufflers I am using on other cars I've tuned, so open exhaust should produce near 350rwhp. I also have a video that I'll work on getting on the computer. I have Sony Vegas 5.0 but don't know how to compress the video when rendering it as an MPEG. Perhaps someone can give me some help on that.

dfinnegan

Geoffrey, can you talk a little more about that drop in torque around 4250? I wouldn't have guessed that it would be that much! What causes that?

Thanks,
dave

burgass

Why the drop in torque?

Smokin

I'm surprised the mufflers conceal that much power. I always thought that a small amount of backpressure helped produce better HP and torque results. I'm sure there is a trade-off somewhere...

Your write-ups are always a pleasure to read! Thanks!

Geoffrey

Remember a few things, this is a completely new car and nothing is ever perfect the first time. I'm openly sharing development of the car and it is far from final. The dyno session purpose is to break the engine in and map it so it can be run on the track. From there things will be adjusted. The current exhaust system was a compromize and not one that I would have purchased, it was given to me. I chose to run it because the car was way too loud to hear any kind of engine noise with the other exhaust and that is critical on a new engine. In fact, I couldn't hear a loose rocker arm until I put this exhaust on. The muffler is one designed to pass Lime Rock Park's 89db limit. It makes the car as quiet as a normal C2 with the primary muffler bypassed. In other words it is restrictive.

The torque drop in this case is a loss of volumetric efficiency of the engine. It can be seen by looking at the main fuel table below. 'Y' axis is throttle position and 'X' axis is engine RPM. The table represents injector pulse width. You can clearly see the engine is using less air where the torque drops. You can see that at lower throttle positions the dip becoms less and less which indicates to me that the exhaust is having a hard time scavaging the cylinder at full throttle. It is not uncommon to see dips in the torque on a N/A engine, but I've never seen one this pronounced. Usually I'll see a 10-15% drop at the most.

The reality is that the engine will be run between 5500 and 8000rpm so this dip won't effect the drivability, but I'd like to correct this nontheless. I'll want to install the straight pipes I have and rerun the car on the dyno and I'd expect better results. I'll also want to try the Champion exhaust I have. But for now, my next step is to get the car on the track and see what other issues arise.

Sire

Wow what good, and gj. Like reading about the car.

JamesE

Ummmm.... MoTec.... Yummie...

Geoffrey

Ok, here is the video. I rendered it using MPEG-1, so hopefully it works for you.

This is the run of the graph above, run from 1500-7800 over about 18 seconds.

Dyno Video - MPEG - 1
Dyno Video - WMV

purplehaze.

Geoffrey -

I tried it several ways and it looks like there are 0 bytes to the file.

Email me the thing and I'll test/post for you if you like.

Glenn

Geoffrey

It should work now. It looks like it didn't get uploaded properly.

purplehaze.

That's the ticket.

Sounds sweet, even with those mufflers.

Hope to see it on the track soon.

Glenn

f11

I'm used to seeing rwhp vs torque crossing at 5250RPM... yours crosses considerably north of 5250rpm, at about 6300rpm - is that an artifact of wheel dynos as opposed to chassis dynos? I thought Dynopack wheel dynos measured rwhp in the purest form using eddy currents as resistance instead of a rotating drum mass, allowing you to tune a fuel/timing map in all cells since the dyno can hold a load or an RPM constant?

Whatever - that's one UGLY torque drop - what was your AFR as you approached, went thru, and exited that region of your maps? Its almost like you were too rich from about 3400 to 4200 rpm... were you measuring EGTs through that region as well? If they fell dramatically with the torque drop, I'd say you were rich.

Geez, that's a sweet sounding audio track!!

Larry Herman

Nice to see it finally running, Geoffrey. Did you do the dyno test at Rick DeMan's shop?