Rev Limiter Question

[DennyMcLain]

The Boss rods are better but they are still forged using powder forging.

Thanks for the information.

Once bought a very expensive block and after later tear down, found out it that I’d been ripped off pretty darn good and as it was full of brand x cheap stuff instead of what I ordered. Being I’d had no issues and it ran like a raped ape, realized that maybe my logic was flawed and it was your classic case of overkill vs intended use. After all, wasn’t racing pro stock or running 30lbs boost.

In thinking things through a bit, I’m sure the regular pistons and rods will work fine and may instead upgrade the heads with porting and lighter components. Believe the Boss is intended on being a road race type car maintaining very high rpm’s for a somewhat extended period and the money probably better spent in other areas.

Betting 7500 rpm in the regular 5.0 block is not a big whoop, but I’ll run it through another program looking at piston speed just to be sure. Thanks again!

 

[Germeezy3]

Thanks for the information.

Once bought a very expensive block and after later tear down, found out it that I’d been ripped off pretty darn good and as it was full of brand x cheap stuff instead of what I ordered. Being I’d had no issues and it ran like a raped ape, realized that maybe my logic was flawed and it was your classic case of overkill vs intended use. After all, wasn’t racing pro stock or running 30lbs boost.

In thinking things through a bit, I’m sure the regular pistons and rods will work fine and may instead upgrade the heads with porting and lighter components. Believe the Boss is intended on being a road race type car maintaining very high rpm’s for a somewhat extended period and the money probably better spent in other areas.

Betting 7500 rpm in the regular 5.0 block is not a big whoop, but I’ll run it through another program looking at piston speed just to be sure. Thanks again!

They are not making any additional power over 7500 rpm, so no need to rev the Boss engines any higher unless you plan on heads and / or cams. For N/A operation lightweight powder forged rods are fine and they don't mind extended high rev situations. They are also proven in competition as the Boss 302R's now have a full season under there belts. If I were you I would almost wait until the Boss engines are actually dynoed to discern if it makes sense to buy the 5.0 GT if the main reason you would buy a Boss is because of the engine.

As of right now what is known is that the intake cams are the same, the difference is the exhaust cams, tuning and the runners in the box intake. Ford Racing said the intake is responsible for just as much of the power as the cams are. Also the Boss has a very agressive non emissions legal track tune that is accessed by the second key. Speculatively I will assume that a standard 5.0 with the Boss intake and an agressive tune is going to make the same or only a little less hp than an actual Boss engine.

 

[BAKnBLK2010]

OK, that's slightly different than what I read. I wish I could find the thread. The way someone described it is that you used the buttons on the steering wheel to change the launch rpm and you could see what changes you were making using one of the digital readouts somewhere on the instrument panel. Has anyone seen this anywhere?

So BAKnBLK, with what you're talking about, how long would it take to make a launch rpm change between rounds at the track?

Just the amount of time it takes to download a tune from the SCT handheld tuner. I've never actually timed how long it takes but I'm guessing about 5 minutes tops.

 

[DennyMcLain]

For N/A operation lightweight powder forged rods are fine and they don't mind extended high rev situations.

If I were you I would almost wait until the Boss engines are actually dynoed to discern if it makes sense to buy the 5.0 GT if the main reason you would buy a Boss is because of the engine.

Speculatively I will assume that a standard 5.0 with the Boss intake and an agressive tune is going to make the same or only a little less hp than an actual Boss engine.

Very good post and in agreement with literally 100% of what you said. Owned a set of Howards powder forged rods with upgraded bolts and 600 at the wheel shifting @ 7200 rpm was not an issue in a stroker motor. Not only "nothing wrong"...."good stuff!"

Right now I've got spec'd out Boss intake and ported heads along with CAI, tuning software, underdrive pulley and exhaust. My gut says the Boss intake and heads will put raise the powerband to probably where I want it. Have to see how the intake to exhaust ratio of the cams works out in the Boss. Fickle area to guess.

Your right, you never know until you know! As a rule of thumb, bottom ends do not make power, they just stay together.

Thanks!

 

[Germeezy3]

No problem, one are that will be difficult is finding a tuner who truly understands the TiVCT tables and how to adjust them. Having listened to a Boss 302R in person right when it starts you can tell the cam timing is very aggressive. It actually has a little bit of lope to it just when its idling. The other benefit to the Boss is that it does have better PM rods which are proven on the track. The standard 5.0 has not had any rod failures with high revs at the drag strip but there is not much data as far as how they will hold up in a road course situation.

The standard concerns that you have with valve events is just not going to be a concern when some of the high lift, extended duration VVT cams come out. Especially coupled with a new philosophy of using the TiVCT to its best advantage instead of locking it out. The surface of this engine has just been scratched and there is more compression and timing to be had once they bring direct injection to this engine. The injector bosses are already there, and I would love to see them drilled for secondary injectors. Port injection at idle and at lower loads and revs, and direct injection where its cylinder cooling effect is used best such as situations of extended high revs.

 

[RectalRampage]

UO

Warren Johnson once said that you should shift 10% beyond where your car makes its most power, so if your making your max power at 6800rpms then you should be shifting at 7480 using his match. I'm sure there is a fudge factor in there but its always worked for me.

Also now that you have a tune and are shifting higher let me know if I can help you when your clutch starts acting up. Our prices are unbeatable on Mcleod's lineup of clutches.

JJ

I will make you a nice website for a free clutch.

 

[beefcake]

Beefcake had detonation @ 7500.....

I had detonation at 8000, and that was on a downshift spike to the limiter, '

i was shifting at 7500 with 0 issues on the upshift,

my problem was tires spinning, got back in it, it downshifted and went right to 8000, that making probably around 600rwhp there as well

 

[Full_Tilt]

So has anybody really established what these engines can be safely reved to (without piston slap or worse)
Im new to these modular engines, but I was pleasantly surprised at the rod ratio (1.62:1), its similar to what you see in some of the higher reving honda engines. Like for instance the F22C with has a rod ratio of 1.65:1 and a factory redline of 8k rpm, while many people rev them to 8500 rpm very reliably.
Im not saying these engines will be able to do that just based on the rod ratio, as it is only one of many factors, but I was hoping upper 7k to 8k may be possible.

 

[RectalRampage]

RPM X STROKE (mm) ÷ 152.4 = Piston Speed (FPM - Feet Per Minute)

Usually the rule of thumb is keeping it below 4,000 FPM for an average DD engine; modern race/performance engines designed to do so exceed this point safely - id say much more then 4,500 is really starting to push it in a DD street car with stock components.

Stock Hard Limit: 7,000 RPMs (rev limit) x 92.7mm stroke ÷ 152.4 = 4,257 FPM

Id probably go with no more then a 7400 hard limit if you want to play it safe.