Let's Play - Predict the HP Game!

[al lkosmal]

That is a nice engine. excellent results.

[jluetjen]

Camgrinder and Tony;
Given the smallish 34 mm ports I suspect that narrowing the lobe angle (and increasing overlap) will actually lose HP because of the intake restriction - inspite of the individual carbs. I've seen comments from Chevy engineers about the Le Mans spec Corvette motors (using the spec'd intake restricters) liking virtually no overlap. Basically, as the rev's climb the pressure in the intake starts to drop below ambiant proportinally with the increase in engine speed. With no overlap, as long as the pressure in the cylinder is less then in the intake when the intake is open, some charge is sucked into the cylinder. If there is overlap, and the exhaust ports have any pressure above the pressures of the intake and cylinder, the exhaust will push the charge back out of the cylinder and intake contaminating the charge.

Personally I think that the engine would respond to bigger intake ports (or 3.2 heads which would accomplish the the same thing) in combination with what camgrinder suggests and possibly larger carb venturi. But in the mean time I'd go out and enjoy the rush as the engine comes on-cam!

[camgrinder]

Are you referring to the American Lemans series C5 corvettes?

[TonyG]

Carrera3.5L

>>>EDIT: If you tell people the motor makes 199 rwhp, then John wins. If you round up (and I know you will) and tell your friends your motor makes 200 rwhp, then I should win, right?<<<

hahah you know it all too well :-)

You'll have to take it up Camgrinder and battle it out. Right now, all I can do is go by the rules set forth on page 1 which stated closest without going over. The way I see it, Camgrinder won it by a "hair".

I'm going to pay it out with a money order mailed to the winner. So... I suggest you open this discussion to the list. In the absense of any discussion about it, I'll have to pay out to Camgrinder.

TonyG

[jluetjen]

Are you referring to the American Lemans series C5 corvettes?

Yes, the 2003 Spec C5-R used both in the ALMS series as well as at Le Mans. According to comments from the Program Manager John Rice published in "Race Engine Technology"...

Considering the valve timing, Rice notes that an air-restricted engine such as this needs "low overlap, short duration and as much lift as you can get". This aggressive valve acceleration comes with the territory.

Apparently in 2003 their engines produced their peak torque at 5200 RPM and the peak HP at 5600 RPM. But in the case of the 'vette, they "have attained the torque curve of a diesel engine!"

[rdane]

Ok I gotta ask...

200 at the wheels makes it 235 at the crank. Interesting Bruce Anderson shows a similar carbed 3.0 SC engine on page 151 that is on an engine dyno showing 210hp and 200# of torque.
Tha engine's HP drops off like Tony's did at 6000. The HP graphs could be duplicates they are so close. The torque curve looks very similar between 4 and 5000rpm but Ton't is much peakier but the number is very good as well when right in comparing it to BA's a engine dyno.

John, why so far off from your original estimate?
Never thought the lower compression pistons would have pulled 200 at the wheels. Never thought Tony woulod get anything like these curves either. Richard Par says the PMOs are a good match to CIS cams...20/21 included.

How come the 20/21 is so peaky in this engine?

Typically the dynos I have seen with a 20/21...all four which isn't many I agree, will get you a long and very flat flat torque curve from 4 to 5500rpm and HP not dropping until 6500.

Good example are these:

red lines are a 20/21 cam on this one


this is a 3.0 with the exhaust and cams but 8.5:1 comprression and CIS


Tony's

[camgrinder]

My guess was based on the carbs increasing HP by 10 over what my guess would have been with cis. To me this is normal when changing from cis to carbs. The torque curve suffers and the increase in HP is alway at the peak. I am still surprised the peak was only at 6000.
My suggestion on closer lobe centers is to increase midrange torque. Adding some duration puts the intake closing and exhaust opening point back to where they need to be.
Cis and motronic systems like 112 to 113 lobe centers, Webers like 98 to 102 lobe centers, and in my opinion PMO carbs like 104 to 108 lobe centers.

[TonyG]

camgrinder

After studying the a/f ratios/dyno chart, it's clear that the midrange can be picked up quite a bit by leaning out the midrange.

However... both Richard at PMO and I agree that there's another 10RWHP with different spark plugs/ignition timing.

But what's going to occur is that I'm going to take out the intake ports to 37mm. I'm trying to find a local porting expert to do the job as we speak (well... earlier today I was).

I'm certain that I can get 220+RWHP out of the 3.0 setup using the existing setup with slightly enlarged intake ports, more timing, and the proper a/f ratios.

The dyno chart I posted was an out-of-the-box setup. No tuning/corrections/or modifications were done to anything after the engine was assembled for the dyno run that was posted (mainly because of the contest...).


TonyG

PS> Email me where you want your prize mailed to.

[Carrera3.5L]

Originally posted by rdane
200 at the wheels makes it 235 at the crank.

rdane,

It doesn't make 200 at the wheels, remember? It makes 199.8, right TonyG?

I don't care about the tank of gas, pay it out to camgrinder.

When a number is >.5, you round up to the next whole number. When it is <.5, you round down. Simple as that.

Ralph

P.S. - Tony, I am going to needle you on this as long as this stays as your current dyno number. BTW, do you have a 2nd run to back up this number? Most guys do 2-3 runs.

[camgrinder]

I would tune the engine before ripping off the heads. Fix the air/fuel ratio, maybe move the cam timing etc. I agree there is at least 10 more hp in your combination.
209.8 hp!

[jluetjen]

200 at the wheels makes it 235 at the crank. Interesting Bruce Anderson shows a similar carbed 3.0 SC engine on page 151 that is on an engine dyno showing 210hp and 200# of torque.

RDane, you and I are in complete agreement! When I was logging the results into my spreadsheet I was copying the numbers over some 3.0 data and they were almost exactly the same! The only difference is that I then adjusted TonyG's data by 15%. BTW, The BA data that you mentioned is in my database also and I too am scratching my head about how TonyG's engine can perform soooo much better.

John, why so far off from your original estimate?

I dunno!

As I mentioned earlier, TonyG's engine is pulling a lot more air though his intakes then I anticipated. I was pretty close to nuts on for the torque engine speed, but underestimated the BMEP's generated by the 20/21 cams. I only had your engine (RDane) for a comparison -- and I don't know how to tell you this -- but this carb'd motor is far better at generating torque for it's capacity then your CIS motor .

I was wrong.

Now that I've got some data points for the 3.0 and 3.2 liter engine sizes I should be closer next time.

I am still scratching my head though about how TonyG's engine's stock heads can outperform almost all of the other 75 configurations in my database. The other exception is Grady's 2.8. I'm still thinking about what is in common with both of those configurations that allows them to flow the extra 4%.

[jluetjen]

BTW TonyG -- Can I ask what you are running for carb jetting?

[rdane]

John I have another 3.0 SC with 20/21s if you want the dyno sheet.

Wrong? Me too obviously..10hp instead of the 5hp I suspected from the carbs but WAY off the graph when it comes to predicting Tony's curves.

Superman's '83 3.0 that was reringed as well, on CIS and 20/21 cams ran a 174# at the wheels for torque. Tony was 185 for a quick refernece. Sup's hit that # at 3800 and held it to 5000 pretty much in a dead flat peak. Sup's peak power fell off slowly after 6000 to 6500 and the rev limiter dropping only 20 hp.

Bruce Anderson's engine dyno for similar SC mods shows 210hp and 200#. Make it 178 and 170 with a 15% loss. Never seen an engine dyno do anything close to only a 15% drop here.

My guess is that Bruce Anderson mixed and matched engine and chassis dynos in his book and then never labeled them.

Like you said, "enjoy the carbed engine coming on cam"....

this carb'd motor is far better at generating torque for it's capacity then your CIS motor

Ya, ya I know but waiting till 4500 rpm seems a little extreme to hit your torgue band?

No offense Tony

[TonyG]

Hey Guys

>>>Ya, ya I know but waiting till 4500 rpm seems a little extreme to hit your torgue band<<<

The thing you have to remember, is that the TQ "dip" between 2500rpms and 4000 rpms is because of the car going far too rich. Once that's fixed ala rejetted, the TQ curve will be much better and much higher between those 2 points (the TQ curve will fill out).

See predicted HP and TQ curve example chart below:



As is it, it feels very linear. There's no "waiting".... and when compared to what the car was stock... it's more powerful, by a large margin, everywhere in the TQ and HP curves.

Lastly, I was not running a lot of timing at 32 degrees total advance. There's definitely more more of both TQ and HP with another 5 degrees total advance.

So like I said... I'm 100% certain that I can get this current combo fattened up in the TQ area, and another at least 10 to 20 RWHP.

After that, I'm going to open up the intake ports and see where that takes me.

TonyG

[rdane]

What model of Dynojet are you running on Tony?

Your current graph looks like a duplicate of Bruce Anderson's carbed 3.0 with CIS cams. Love to see you get the one you are speculating.

220 rwhp will be a good feat from a basically stock 3.0.

[TonyG]

Carrera3.5L

I am willing to go with what ever the people on this board decide with respect to the winner.

Ask the "crowd" who won...

TonyG

[rdane]

No question Camgrinder......199.81 aint 200 even in Seattle

[TonyG]

jluetjen

>>>Can I ask what you are running for carb jetting?<<<

Currently the mains are 150 (I don't know what the others are).

I'm going to go down to 140 (or 145) than take down the air correctors by 5 to correct the top end lean condition that will be created by the smaller main jets.

TonyG

[TonyG]

rdane

Here's the information on the dyno:

DynoJet 224X with Data Aquisition running WinPep 7 software.

I wanted to run on a 248 DynoJet, but both places local to me are out of business... so I had to go to the next closest place that's running a DynoJet (DC Performance in Los Angeles).


TonyG

[rdane]

That helps, thanks. Not a good comparison on our data bases without a couple of pulls on the 248 although Chris at Dynojet will tell you there is virtually no difference, I have seem a bunch when comparing the two.