End of the Volvo big block motors......

[FormulaFanMN]

Re: End of the Volvo big block motors......

Gear ratio on the 496 and new 502 is a 2.0. With that, your number change drastically. What formula are you using for the propshaft torque? Torque for marine engines has always measured at the crank and horsepower at the propshaft.

 

[QC]

Re: End of the Volvo big block motors......

I still think you're missing the point. The engine capability is the discussion, at least I think it is. Merc doesn't offer the 6.0, so a little hard to make an Apples to Apples comparison, but propshaft RPM is what determines prop sets right?

I used the numbers you provided. So at the crank for torque, and propshaft for the horsepower. Since we are using crank torque numbers, then my propshaft torque numbers are slightly over stated for both as there are gear-train losses of somewhere around 6 - 8%, but the losses will be similar for both examples so left it alone as it is an unknown. The calc is torque x gear ratio = propshaft torque. RPM is opposite. Very simple calcs. Gear reduction of 2.0 = double the torque and half the RPM etc. Regardless of the application.

Oh, and marine engines are not rated uniquely. I/Os are All other applications of Inboards are crank and crank. Most marine manufacturers do not publish torque numbers because they confuse the discussion. As I have said, peak torque is not in play for prop load "curves" although climbing the bow wave changes that discussion. I have another chart I will post later that may help you with that.

 

[FormulaFanMN]

Re: End of the Volvo big block motors......

Merc won't be using the 6.0 ever. They have the 502 production from GM performance division, so Volvo had to use what GM was currently producing.

QC, look forward to more info.

Good info

 

[FormulaFanMN]

Re: End of the Volvo big block motors......

QC,

Is there a way to estimate what speed the 6.0 Volvo be give me on that example I talked about above?

Do the Volvo claims on acceleration based solely on the reduced weight of the 6.0 over their old 8.1? Obviously the numbers we talked about show reduced torque, but obviously Volvo is claiming reduced acceleration times. I know when the 6.2 came out it smoked the old 7.4 in acceleration times.

 

[QC]

Re: End of the Volvo big block motors......

What are you running the 380 502s in? What speed do they run?

 

[FormulaFanMN]

Re: End of the Volvo big block motors......

I will post the numbers I have with both the 377 mag and 8.2. It's in a 2013 formula 350ss / 350 CBR.

 

[QC]

Re: End of the Volvo big block motors......

If the numbers are correct, and the ratios and propset are somehow equalized. And the WOT RPM is right, and the boats are in all other ways equal. Then the 6.0's should be slightly faster than the 502 due to weight. In my example, with the wide disparity in gear ratios, then the hole shot should be similar as well. However, you are comparing Bravo 3s to DPs etc. Brings in a lot of variables. But it doesn't matter if it is a 70,000 RPM turbine with 17 lb ft of torque (don't do the math, I made it up, but we could speculate on this for fun), if it was geared right, and that developed horsepower to turn the shaft to plane the boat and then to maintain top speed, you could expect similar results. Yes, higher peak torque values will improve performance if ALL ELSE is the same. In this case the gear ratio, or propeller, and weight, AND, most importantly the RPM is different, so the horsepower at peak torque RPM is similar, so the performance when geared correctly is also similar.

 

[rbh]

Re: End of the Volvo big block motors......

A "Q" for QC.

Why is it when you see a spec/dyno sheet for an engine it will develop X amount of max torque at X RPM's and the engine will develop X horsepower at X RPM's but neither amount is at max RPM,s?

Is the marine engine cammed for horse power and torque at the top of the RPM scale?
I know you can move the performance curve around alot if you tuned the exhaust (cut to length), but how does that effect a motor that just has water cooled manifolds?


Thanks

 

[QC]

Re: End of the Volvo big block motors......

The whole answer is HP = torque x RPM/5252. If torque falls off faster than RPM horsepower drops (at the top). If torque rises very steeply (at the bottom) then peak horsepower may actually be down near peak torque. The problem, ,is that people try to separate these three (torque, RPM and horsepower). You need all three to do ANYTHING!! Alone, the only one that really matters is horsepower.

 

[Tail_Gunner]

Re: End of the Volvo big block motors......

The whole answer is HP = torque x RPM/5252. If torque falls off faster than RPM horsepower drops (at the top). If torque rises very steeply (at the bottom) then peak horsepower may actually be down near peak torque. The problem, ,is that people try to separate these three (torque, RPM and horsepower). You need all three to do ANYTHING!! Alone, the only one that really matters is horsepower.

Here QC have some fun with this...Touqre provide's accleration.. In the end that is what it does know matter how you look at it. This whole conversation has been centered around that. The question is how to marry big tourqe and high rpm those two come at a very high price usally one settles for one or the other..that depends on application.

In this case Volvo it seems will use gearing and the question that comes to mind is 6000 rpm. Is that bad...no if the drive has been designed to withstand that. The LS engine is leap over the 8.1 but the old displacement thought keeps sticking up it's old ugly head.

It seems your trying to define how a motor is built by using the method to measure its power. In every case wether gas of deisel both are going to use differnt builds...similar but differnt. The terms being used here are merely a measure of the outcome.

 

[QC]

Re: End of the Volvo big block motors......

Torque provides acceleration.

Only if maintained over a "curve", and if the curve is based on RPM, which means there is time included (the M), then we are discussing horsepower.

It seems your trying to define how a motor is built by using the method to measure its power.

No, I am simply trying to predict performance based on the stated numbers produced by an engine. Just because one engine has higher peak torque than another doesn't mean it will perform "better". We are concerned with propshaft torque and horsepower, not necessarily engine torque and horsepower. The prop(s) don't know and don't care what's twisting them.

 

[Scott Danforth]

Re: End of the Volvo big block motors......

guys, remember that the L98 engine (6.0 liter) can have the block swapped with the LS3 or LS7 or even the LSA or LS9.

I agree that the LS motors are leaps ahead of the old iron big blocks, and they respond extremely well to performance upgrades.

 

[rbh]

Re: End of the Volvo big block motors......

guys, remember that the L98 engine (6.0 liter) can have the block swapped with the LS3 or LS7 or even the LSA or LS9.

I agree that the LS motors are leaps ahead of the old iron big blocks, and they respond extremely well to performance upgrades.

Please find me a couple of 351c 4v marines then please...

 

[Scott Danforth]

Re: End of the Volvo big block motors......

finding a commonly available LS motor is going to be much easier than a motor that has been out of production for 28 years.

 

[rbh]

Re: End of the Volvo big block motors......

finding a commonly available LS motor is going to be much easier than a motor that has been out of production for 28 years.

Try 39 years, those engines were enginered to make torque/Horse power at at the top of their power curve.
Over sized ports and valves, they made the power were it was made to be on the track or water.

 

[Scott Danforth]

Re: End of the Volvo big block motors......

the 351 was in production from 1969 thru 1985. granted, with wet manifolds from mercruiser was 70-75

 

[rbh]

Re: End of the Volvo big block motors......

the 351 was in production from 1969 thru 1985. granted, with wet manifolds from mercruiser was 70-75

"NOPE", I am talking Cleveland 4V or BOSS or HO, not the modified or the windser.
They quite making these guys in 1972 for 73.
Production run 1969/1970-72/73.
Small block heads flowed more than the big bore equivelent. (actually to much flow, no bottom end)

 

[QC]

Re: End of the Volvo big block motors......

Here's the chart I referred to earlier. These are for a Cummins diesel, but the point is the same. The lower line on all three is what a prop requires in power, torque and fuel to turn it. The higher lines are the engine's capability. Looking at any of them, you can see that the prop does not require all of the available power to turn a prop at most speeds. These types of charts do not assume the high load point of climbing the bow wave to get on plane, because there is no way to predict that point unless you are dealing with one specific hull. But again, you never experience the top line ever unless the throttles are mashed:

 

[QC]

Re: End of the Volvo big block motors......

Some more good info here: http://www.boattest.com/engine-review/Volvo-Penta/4500018_V8-380_2012

 

[Tail_Gunner]

Re: End of the Volvo big block motors......

Some more good info here: http://www.boattest.com/engine-review/Volvo-Penta/4500018_V8-380_2012

Nice link QC it shows the differnt build tech and how the engine makes power.

The cam phaser assembly automatically advances or retards the valve timing for more consistent performance throughout the power curve.

Variable valve timing adjusts the valves dynamically throughout the power curve to increase performance. (Chart and data supplied by Volvo Penta.)
A flatter torque curve provides lower planing times and better midrange response plus the WOT range is less load sensitive. Combine this with a 2.14:1 gear ratio, increasing the gear ratio up from 1.78:1, and the result is superior acceleration potential, even in heavier boats, says Volvo. This allows for use of the improved DPS drives with a ratio between 1.95 and 2.14. Volvo Penta tells us that the spread in performance between the old power plants and this new V8-380 gets further and further apart the more the boats are loaded.

In essence the 6.0 has a far superior head design and a hot cam tamed down a bit with the phaser. Now if that engine had direct injection and twin tubo's ....Again wait for the 5.0 ecoboost it will stun the auto indrustry...And with with respect to GM if they are still the company they once were they in turn will build another stunner.