ShawnSmith

OK folks,

After many months of anticipation, I have a real live example of a Greg Brown 6.5L 928 in my garage. There's a long and entertaining story to this ongoing project, which I'll include below. For those with less attention span, here's the executive summary:

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6.5L motor upgrade completed. 19 pound injectors are maxed out, and the car lacks LSD, thus a wheel is slipping on formal dyno runs. Present measurable performance is ballpark 350 rwhp and 430 rwtq. We're gonna put 1200 miles on it for break-in, then swap 24 pound injectors, add an LSD, and re-tune. At the same time, tests will be run to measure the improvements from intake spacers, and from a revised set of exhaust cams. We expect to post significantly higher hp numbers within a month. Gregs work on the brakes, suspension and exhaust are glorious. I'm very happy.

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OK, now for those who like a good story and details.

I bribed my friend Glenn (with promises of free tire-smoke inhalation) to ferry me over to Greg's shop today so I could pick up the completed car prior to new year's.

Greg took us on an extended tour of the completed car, as he carefully sprayed and cleaned the _insides_ of my wheels as the car was aloft on the lift. Yes, the inside rims of my wheels are (or were prior to the drive home) spotless and free of the least hint of brake dust.

The exhaust system is gorgeous - a hand built x-pipe, into a pair of high flow cats, followed by two extra large magnaflows, and then dual plumbing all the way to a pair of neatly trimmed and placed exhaust tips. All of it in mandrel-bent stainless, tig welded.

I noticed a shiny new aluminum undertray, and asked about it. Oh - that's my original tray - they just cleaned the living daylights out of it prior to putting it back on. Similar story for the vents on the forward tray - they'd been a bit askew so they re-revited them into proper position.

Bilsteins front and rear looked nice in shiny silver.

New front rotors still had that wonderful cross-hatch of freshly machined metal on them. Turns out my car had lacked the appropriate brake pad shims that help keep things quiet - Greg added them.

The oil pan had been dropped to help keep the collecting oil away from the new longer cranks. I must remember to measure the oil-full line a few fractions of an inch lower. Oh, and here's a spare quart of oil in case it needs any, which it shouldn't.

The motor is where most of the money went, and amusingly there's not much to see, at least not yet. My intake and cam covers are there, still sporting original porsche silver paint, and hiding the longer crank, bigger pistons, valves, lifters, and hours upon hours of careful grinder work. Lift the hood, and the thing really does look bone stock, which was one of the goals of this project.

Fire it up, and the ever-so-slightly lumpy throttle burbles with an exhaust note that pleases me. After much negotiation, Greg has delivered a loudness that is very slightly quieter than my stock S4 was with an RMB, and a bit louder than that setup under heavy throttle. I can burble around under light load and not really draw too much attention, yet it still bellows V8 goodness when you get it on cam. Perfect!

Now on to details of performance, dynos, and break-in.

The car presently has 19 pound injectors, which wound up being maxed out at 100% duty cycle on dyno tuning. Since we already plan to do further tuning after 1200 miles of break-in, Greg left the 19 pounders in place, and decided not to worry about the less-than-possible early dyno runs.

An additional reason for not worrying about the dyno runs was wheel slip from lack of LSD. Although I had believed the car to have the limited rear slip, Greg's patient hand points to the "1" on the tranny that indicates otherwise, and a single-spinning wheel under full throttle agrees with his diagnosis. Similar issues happened on the dyno. As the car built to above 400 rwtq, one wheel escaped and the run was no longer reflecting reality.

So the "baseline" is somewhere in the region of 350 rwhp and 430 rwtq, with the disclaimers that tuning is not final, a couple more things are gonna be added, and we're gonna get that second wheel in on the game of pushing the dyno wheel properly.

The original goal for this project was a street sleeper. Not visually or acoustically offensive, great big bags of torque, and a challenge to get into the upper 300's for hp, nearing 400 rwhp. Since that time, I have learned tons about the limits of the stock intake, and losses through the automatic transmission. 20% slushbox loss means 400 rwhp would require a full 500 hp at the crank - somewhat beyond what Greg feels the stock intake can support.

But we have a plan....

I'm gonna drive this already wildly enjoyable beast for 1000-odd miles and get it broken in. Greg's gonna have his 24 pound injectors, a refurbished LSD, his shark tuner, and a couple of new parts ready when I return later in January.

We're gonna do a series of tests, including at least one which you folks should enjoy.

Firstly we're gonna get the LSD and 24 pound injectors in place so we can get accurate figures on where we're really at.

Then we're gonna add.... Intake Spacers! Everyone wants to know if widening the intake helps big stroker motors? The plan is to get a good clean A/B run on my motor to find out - is there a difference, and if so, how big is it on this style of motor?

Secondly, a revised exhaust cam is planned. Again with before/after dyno tests.

Greg is excited about several aspects of how the motor is already performing, and thinks he can take a solid shot at making the strongest California-legal, stock intake, street oriented auto-trans motor that's come out of his shop. He indicates that the slush-boxes tend to dyno around 15% lower than the stick shifts. If so, we've got some serious work to do. Below is his reference dyno run for a stick shift 6.5L of similar, although one-generation-older work from his shop.

Please note - this is NOT my motor - it's a stick shift, and so we'd round these numbers down from the ~423 rwhp to more like 360 rwhp on a auto-trans. However Greg thinks we can maybe push the limit a bit with some of his new ingredients.

380 CA-legal, stock-intake, slushbox rwhp might be do-able. Or maybe a bit more. I'll have formal dyno runs for you all on my motor in a few weeks. Meanwhile I'll be learning to tame the 350-ish hp that I already have to contend with.

PS Yokohama tiresmoke is kinda stinky

ShawnSmith

Ah - I forgot to mention the part where I handed over my firstborn, and signed a futures contract on my second born child for all this work

RyanPerrella

i must say, i am surprised at the huge drop in power for the automatic

hacker-pschorr

Sounds like an awesome project!!! Thanks for sharing.

Are you using the stock LH/EZK with the Sharktuner?

andy-gts

Thanks for the write up! Always great to follow along with fellow enthusiasts. the numbers seem pretty conservative...when will you dyno_ after the 24 lbs injectors, sharktuning and intake spacers?
andy

toofast928

Good job! Now with the remaining winter months need to install a Supercharger.

CanAmJohn

Me too? Once the TC has locked up, why would you lose so much more in the transmition?

Sounds like a really great torquey drive you'll have there!

ShawnSmith

Next dyno runs should be towards the end of January - it'll take me a few weeks to put the break in miles on it, then I have to schedule time back at GB's to do the differential and injector swap followed by assorted tests and tuning.

bronto

Ha!, note this is in southern cal, where it's dry, 65 with a low of 45 tonight, and was still fire season until a few weeks ago. "Winter months" is a term that has no meaning here...

ShawnSmith

I'm not a transmission efficiency expert. By reverse-engineering Greg's estimates on rwhp vs crank hp, my best understanding is that the 928's auto trans has roughly 20% loss. To get 400 rwhp, you'd need 500 crank hp (500 - 20% of 500 is 400).

Conversely, it appears that at least in whichever gear the stick-shift cars are tested, the manual gearbox only experiences a 10% or 12% loss, thus the above 423 rwhp stick motor is making around 475 crank hp.

I agree the difference looks huge. Some of it may be in how the tests are performed (does one lock the auto trans into the most efficient 4th gear?).

Anyhow, the thing already flies. I consider these weeks at 350-ish rwhp to be excellent training-wheels time while we prepare to add the next chunk of power.

ShawnSmith

Oh - FYI, I managed 19.5 mpg on the highway drive home (traffic limited use of heavy throttle, but it's nice to see the monster motor can still be efficient).

jcorenman

Shawn,

Great info, Great project! Many thanks for posting this, and please keep us updated as the project progresses.

Rick Carter

Thanks for sharing, it looks like you got what you wanted a killer street motor that looks stock.

123quattro

Automatic transmissions have more losses for a couple reasons. If the convertor doesn't totally lock, there is a loss. The pump is always running to pressurize the clutches/brakes. This is several kWs of loss there that does not exist in a manual. The non-engaged clutches also have spin losses associated with them that are an inefficiency over a manual. Generally autos have about 6% more loss than a manual equivalent.

Darien

Great job...you could actually benefit from bigger injectors with the sharktuner...Once you get the LH and EZK sharktuned, then you'll see the full pontential of your beast