Weiand 871 vs. Vortech YSI on the dyno,no contest!

[oldhead]

I took my SBC to the dyno with a 871,made 30 pulls besting with 748hp. at 6600 & 6900,Tq. 637 at 5100,Started spraying with nitrous,12 pulls later with 225 jetting,952 hp. at 6700.Tq.860 at 4900..That was back in 4-02...this April went back with a Vortech YSI...1004hp. at 7000(it wanted to go higher),Tq.768 at 6600,with a 125 shot 1130 hp.at 7000,TQ. over 880 from 5800 to6700....My question is "Why is the r"s so high on the Tq.? I have a very mild cam 248-260 at .050???OLDHEAD

[oldhead]

A second question: Would the car run faster if the peak tq. was at lower rpm. By the way I had another pulley try that would have made more hp. and would have "Red lined" the blower at 7000...OLDHEAD Ps; no intercooler...

[Ron E]

I believe so long as your gears,converter are in sync with your rpm, the higher tq rpm, especially with a larger number will have more potential (I'm looking at the no-nitrous numbers)
You said with the Vortec, it "wanted to go higher" . Does that mean it possibly didn't peak? Wondering because the peaks are so close with the Vortec. How "flat" is the tq curve leading up to the peak with the Vortec?
Just wondering, was the boost on each blower close?, was the vortec intercooled?

Those centrifugals make great power, Since I suck at bending pipe, they're my favorite power adder.




Sorry, not fluent enough with forced induction, to even guess at your tq-peak/RPM question.

[oldhead]

Ron; no intercooler....Tq. starting at 5800 by 200's 742,750,759,764,768,762 and at 7000,752....871 drive ratio(over)boost and hp.at 6700...13ov,16#,748hp-19ov,19#,723hp(loss).....YSI boost and hp...14#,877hp-213,1004hp.....Do you have a blower? I have had 5 blowers on my Monte(B&M 144,162,250) plus the 871 & YSI....I owned 14 supercharged cars,The first in 1960.I am 69 yo....OLDHEAD

[Ron E]

My last one was a '90 mustang 5.0. (Real entry level stuff). I added a procharger/I-cooler at around 115K, and the poor old body was worn out, from the miles, and a couple of wrecks, and retired it at 197K. The same blower will go back into service before long.

[Jay Allen]

My question is "Why is the r"s so high on the Tq.? I have a very mild cam 248-260 at .050?

I'll bet if you set and calculate pulley ratios and then calculate blower speed, you'll find that peak tq occurred at peak blower speed (or VERY close to it).

[oldhead]

Let me get my dyno slips out,these will be with diffent pulleys; pulley34t,Tq.627 at 7000-pulley30t,768 at 6600-pulley28t,783 at6100............max. hp. was at where the pulls were stopped at 7000 they were 835,1004 and 999.....The reason hp was down on last pull, mixture richened to be safe...I did not use my 27t pulley which would have red lined the blower at 7000........So I don't think you are right,,,but THANKS anyway......OLDHEAD .....PS; boost was 14, 19 and 22#

[Jay Allen]

pulley34t,Tq.627 at 7000
pulley30t,768 at 6600
pulley28t,783 at6100
I did not use my 27t pulley which would have red lined the blower at 7000

or VERY close to it

I'd say w/o knowing TONS more about your combination, 400 RPM (+/-200) is pretty close.

[oldhead]

Sorry to tired tonite,Going to the dyno tomorrow a 632 bbc.talk more Friday.OLDHEAD

[SStrokerAce]

Oldhead.... I wouldn't be scared of the 27T pulley... the YSi blower can easily be overspead 10% without problems or so I hear so pushing it to it's limit at 7000rpm shouldn't be a problem. Remember these guys design these things to have gear heads play with them.... our typical motto is "if some is good, more must be better and a lot must be just right"

Bret

[oldhead]

Hi, about my engine comb.(It takes me for ever to type) would you please go to www.enginecombination.com to see my spec's OLDHEAD

[bob cook]

I thought I'd mention that I'm running my YSI above 70,000rpm on every pass. I've had it up to 80,000. I know there are other NMRA Renegade cars doing this on a regular basis. I think the record is mid 90,000rpms and it stayed in one piece. We do this without an intercooler. The air temps reach 300 degrees through the traps. We are using 8 rib serpentine belts and there is some slip occuring. I wouldn't worry about spinning it faster. We are also seeing 30+ pounds of boost.

[oldhead]

Bob; I want to thank you for the great info.,I will sleep better knowing I am not pushing my blower to much....Could I ask you more about how you are doing so well with out a intercooler.....I found that at the boost levels I have used(14,19,21#) that my Sbc.400 likes the timing up at 32, and might want more. I use C16 fuel. Was you peak hp. and tq. close like mine. Can I ask what cam you have?..Thanks OLDHEAD

[Jay Allen]

Can I ask what cam you have?

The class he speaks about is called Renegade in the NMRA. All of those cams are a max lift of .550" as measured at the retainer at zero lash. And, all of those cams are hydraulic rollers too.

I have seen engines that have pk tq at 4800 & pk hp at 6300 go absolutely nuts when you add the blower. The one kid in the south whom I did a cam for moved his peak tq to 6600 RPM & pk hp to 8100 RPM. Its all about the blower at that point. The engine is a long for the ride.

[bob cook]

I'm running VP C16 also. The timing crossing the line is 22 to 23 degrees. I would bet that every car in the class that is going fast is on the edge of detonation. I don't have a dyno sheet handy but, I remember peak HP in the low 7,000 range. I normally shift at 7,300. I have a PMS piggyback system to program the fuel and timing. I use an Aeromotive 1:1 boost reference fuel pressure regulator with 83lb injectors. I also use a 3-bar MAP sensor and pull timing out as the boost pressure increases. At max boost I pull 13 degrees out of it. I'm running a Comp Cams .545 lift 244/256 @.05 with 113 degree of lobe seperation currently. I have a new cam on the way for the next event in Columbus. I've done some serious lightening of the valve train and will be pushing the RPM range up a bit. It's hard to get testing in with 9 events so, I'm usually testing during qualifying.