Hi Folks, I am looking for 308 dyno curves for stock or slightly modified engines, any 308 model will do as long as it is identified, ie GT4, GTS, GTSi, GTB, GTBi, QV, etc But what I am really looking for are dyno curves or dyno plots that start near zero rpm, ie at or near idle, below 1000 rpm. All of the dyno plots I have seen on the internet so far start at 3500 rpm or 4000 rpm, and I feel like I am looking at a sales pitch for some before and after mod, that only applies to the narrow band they want me to look at,, its not real engineering, just marketing. thanks in advance Andrew
There's a reason why the plots start at roughly 3k... You won't find them starting from idle. WOT Dyno pull in 4th gear precludes idle rpm loading. Engine Dyno tuning is also the same, start rpm is always 3k for WOT pulls. Steady state is different, we can load for any rpm... But it'll only be for that rpm point, not a pull graph. All that aside, there's loads of dyno graphs posted on here over the yrs.
I've had chassis (rear wheel) dyno pulls start at about 1500 RPM, but it is motor dependent, you often can't get a motor to "pull" in top gear below 3K RPM. I can't place my hands on it, or find it on my computer, But I ran across a chassis dyno run on my 308 not long ago, back when it was still 3 liter. IIRC, max RWHP was about 175HP, but that's all i can tell you. For reference, here is a chassis dyno pull in my '61 Corvette with its large small block motor dialing in the AFR. It starts about 1500 RPM. Doug Image Unavailable, Please Login Doug
I don't like loading below 2500.. prefer 3k.. thrust scalar charts explain it better. 4th below 3k is chugging... Falls right on it face under load and doesn't help with tuning. Get up near 4L and it's not as bad. I don't see the point though given the thrust scalar of the gear ratios. 7L with a slush box... Sure let'er rip!
"4th below 3k is chugging..." Agree re dyno pulls/3000 RPM but one of the things that most impressed me with the 328 is its ability to pull from 1500RPM in 4th gear with absolutely no difficulty/drama/jerkiness. Heck, I've had plenty of US muscle cars with way more power/torque that couldn't do that!
This one starts at about 2250. Maybe not as low as you wanted but closer. High compression, stock displacement, carburetor 308 with early cams. Built by rifledriver and tuned by Aaron at ATS. I believe the torque is very good for a stock displacement engine. Over 170 foot-pounds at 2500 rpm. On an Inertia chassis dyno (like most Dynojets), it is hard for the operator to get everything rolling without jerking and abusing the car. Aaron has a lot of experience with this drivetrain on a chassis dyno, so below this RPM would be difficult I think. Eddy current dynos (like Mustangs) may have a little more latitude.
One point to be made is there are engine dyno charts, with the engine crank shaft/flywheel tied directly to the dyno, and with open exhaust no mufflers or cats, and usually no water pump or alternator load. Its also where you see those splashs on car rag covers: "Get 600HP from your 350 CI Chevy" numbers come from. I assume engine only is what the published factory Ferrari HP/Tg numbers come from? And most F-car dyno charts I have seen are through the transaxle with the water pump and alternator are belted up and through full exhaust. Those numbers will always be 10-15% lower than an engine alone dyno as mentioned in my first paragraph. Doug
Any time you use a chassis dyno, as you pointed out, you are dealing with the drivetrain power loss, tire slippage, different final drive ratios, choice of gear to do the dyno pull, etc. Published HP figure for an engine by a shop or manufacturer is always going to be measured on an engine dyno because there are too many variables on the chassis dyno. The identical engine dropped into two cars with different gear ratios, tire diameters, accessories final drive ratios, etc, will have noticeably different results. Inertial dynos are fun at a Sunday afternoon Harley Davidson picnic "dyno shootout" but for serious engine work as opposed to bragging rights over beer and hot dogs - It's Mustang and similar dynos.
This is legit one of the things that sold me on my gt4 when I went to test drive it. Chugging along behind some slower traffic at 1500 in 5th. They speed up slightly and the car didn't give a single care in the world I was asking it to lift from 0 extension, it just did it. Realy reminded me of a modern mustang in the way that torque truly was just rpm invariable (and it did it with like sub 1/2 the power, invariable cams, and carbs which! which just got me even more convinced I need to spend the next couple months dicking around with the carbs/cams/timing on my daily)
While the engine can chug and move the vehicle along, please don't subject these engines to high gear, low rpm loading. They are not designed for it, it carbon fouls and increases the stress and wear on the engine. The cam profile, esp on the early carb series has a fair amount of overlap, that's why it's not running strong at low rpm but absolutely screams above 5k. In all my yrs of Dyno tuning, chassis and engine, WOT pulls are done from 3k. Chassis pulls really can't get below that as you have to work up to 4th gear before the loading starts. Letting the rpm fall below 2k can risk stalling the engine, I'll let drop to just about 2k then it's WOT.. and at 3k the Dyno loads and starts recording. Engine pulls are different. A bit more complex and I'd rather spend the time point loading and tunning below 3k. WOT pulls are useful to a certain degree, fun for sure.
Yes. Cruising in 5th is going to be what it is on the highway. But in general 3k and up is better. My DD is an old Mercedes with the i6 3L... Highway cruising is 3k at 70 and nearly 4k at 80, it'll run that for days with zero issue. It was designed around that for long Autobahn runs. The i6 is a tq monster but the sweet spot is 4k to 6k, really loves to stretch it legs. Same goes for the Ferraris, high rpm running, better response, more tq and less fouling. Of course it means more fuel use... But when was that ever a concern? 3,4 &6k rpm running isn't going hurt the engine. It's noisy... But that's the best part!
