which motor would make more power

[JMortensen]

Well all I can tell you is that my wife felt comfortable enough to get a little sideways getting on the freeway with the SU's, and when I switched to the triples she was literally too scared to drive the car. It was a BIG power increase.

 

I think Dan Baldwin dynoed before and after switching from 2" Jag SU's to triples. Maybe he'll pipe up...

[Guest bastaad525]

I think Dan Baldwin dynoed before and after switching from 2" Jag SU's to triples. Maybe he'll pipe up...

 

THAT I'd like to hear as I'm convinced the 2" SU's would probably come very close to the power of the tripples vs. stock SU's. I was actually set on doing the 2" SU's before I went turbo. I havent heard any dyno numbers but I've talked to a couple guys who have the Jag SU's on rebello built motors and LOVE them.

[Silent]

im stickin with su's because ima simple kinda guy. im searchin for a decent set of jag su's now. im not in the mood at this point to drop 800 bucks on a set of prepped rebello su's for my car.

 

i love the idea of triples, but spending 600 bucks in jets, 1200 bucks in carbs. almost 2 grand into the fuel side of it all. so i don't have that extra 15 hp from triples. i can live with that. as far as not having any top end from su's? um, no.

[Guest bastaad525]

SU's don't fall flat on top, an L28's stock head and cam do that for you

 

I'm really honestly surprised we don't have more members here running the big bore SU's, but I swear I remember at least ONE member who had links to a webpage of what was truly an awesome L6 Z... I think it was 3.1 or 3.2, really built up, I think he bought the whole built engine from Rebello, and had the 2" SU's and I think made 275 hp to the wheels?

 

It's been a LONNNNNG time but I remember I had some email conversations with said member asking what all the whole setup cost him (I think it was either $5000 or $7000). I do remember he LOVED the SU's and it was that conversation that lead me to want those SU's for myself.

[JMortensen]

SU's don't fall flat on top, an L28's stock head and cam do that for you

I can only relate my experience, but that wasn't it. I had mild porting, big valve E31, and a medium cam and although you could hit 7000 rpm, it was a waste of time going much above 6200 with the SU's.

I think it was 3.1 or 3.2, really built up, I think he bought the whole built engine from Rebello, and had the 2" SU's and I think made 275 hp to the wheels?

Rebello puts their engines on their engine dyno, not a chassis dyno. If I saw a dyno chart that showed 275 whp for any L series running SU's big bore or otherwise I would need to see that dyno recalibrated and the car run again. johnc only made 287whp with MOTEC FI on a Sunbelt engine that was $25K or more IIRC.

[Mack]

I had a 240Z that was poorly tuned with a set of 40MM running an N42/N47 set-up. no cam that I could tell... anyway, the car was fast and had plenty of snort. It would get up and haul *** with the best of them. It could cook tires in a few gears. It did have a fiar bit more HP than a stock N42/N47 would. Ive had a few of those as well. I know the 240Z body is lighter than the 280Z body, but Ive driven other swapped L28 cars and i can tell you 40MM's made a difference. these were DCOE18's sitting on a cannon straight loing runner manifold.

[JMortensen]

Sounds like they were at least in the ballpark Mack. I think a lot of guys as we've said in so many posts can't tune triples to save their ***. So they throw them on, are disappointed because they don't know how to get them running right, then take them off and post a "triples suck" thread on the internet. Ed, I'm thinking of you buddy... hope that MS system works better for you. I had my teething issues as well, but I had a little help from some people who knew enough to get me through. Not that it's any scientifically verifiable proof or anything, but I believe the Mikuni ads quoted a 25% increase in power on an L24 and a 20% increase on an L28. My experience tends to back that figure up.

[Guest bastaad525]

um... 20% of a stock L28's power doesnt' equal 40hp

 

well I don't really have enough of my own data to debate this any further. Make no mistake, I'm not one of the guys who goes around saying tripples suck, I just think they aren't great to use on a bone stock motor and head. With any kind of work, cam, or whatever, something to increase flow, then yeah I think tripples are worth the money and effort. I do think there is NO point to put on tripples if you aren't going to go to a dyno and properly tune them. I would never expect to throw them on and tune by feel and expect them to run well. As far as they make this much or that much power or so big of a difference, it's really all hearsay IMO... no disrespect to your butt dyno impressions guys, but I need to see some real 'proof' before I can believe they would make anywhere near 40hp.

 

I just love the SU's for their simplicity, and I think I'd take big bore SU's over tripples for that reason, even if they didn't make as much power.

 

I can't back up that 275 hp on SU's thing, I wouldn't know where to begin to look. But, I'm 99% sure there is another member on here who has in his sig that he made 270 whp + on a stroker with tripples, now I've seen that guy post in threads I've been in so I'll look for him and his sig. I didn't get the impression that it was a $25k setup either....

[Guest norm[T12SDSUD]]

I've raced tons of guys with triples on their Z's and Brian with the Rebello motor and triples is the only street driven N/A L6 motor I know of that has beaten my Z with SU's and he has a hell of a more radical build than my car.

 

I think SU's are the superior carb for a street driven Z car. if you are looking at road racing with very high speeds then I'd say the triples are the better carb.

 

Later,Norm

[Guest bastaad525]

']I've raced tons of guys with triples on their Z's and Brian with the Rebello motor and triples is the only street driven N/A L6 motor I know of that has beaten my Z with SU's and he has a hell of a more radical build than my car.

 

I think SU's are the superior carb for a street driven Z car. if you are looking at road racing with very high speeds then I'd say the triples are the better carb.

 

Later' date='Norm[/quote']

 

You know, much as I do believe that tripples should work better on any built up L6 with head work and cam, it is kinda hard to argue with Norms argument here I haven't seen or heard of any tripple carb'd cars running faster than Norm other than the one he just mentioned himself. That's the real sucky part here is this weird lack of any kind of dyno test or track test data... knowing how many guys are out there running trips, where are all the numbers showing just how much better they (supposedly) are?

[Guest bastaad525]

sorry for the double post but I found the guy I was looking for, briann510, in his sig he has listed: "1973 240z 3.2 stroker with triple Mikunis 278 RWHP."

 

and links to a website for his car here: http://www.bbgraphics1.com/73z/index.html

 

Just going over the list of what he's got in his motor it's hard to gauge cost but doesnt' look like no $25,000. That's with tripple 44's anyways.

 

Also, Norms 1/4 mile time and trap speed indicate he's putting a good 230hp to the wheels (just guessing at his race weight), on stock bore modified SU's on a 2.9L. That fact together with briann510's example... I think makes it not that far of a reach for big bore SU's on a worked stroker to get near 270 rwhp.

[JMortensen]

sorry for the double post but I found the guy I was looking for' date=' briann510, in his sig he has listed: "1973 240z 3.2 stroker with triple Mikunis 278 RWHP."

 

and links to a website for his car here: http://www.bbgraphics1.com/73z/index.html

 

Just going over the list of what he's got in his motor it's hard to gauge cost but doesnt' look like no $25,000. That's with tripple 44's anyways.

 

Also, Norms 1/4 mile time and trap speed indicate he's putting a good 230hp to the wheels (just guessing at his race weight), on stock bore modified SU's on a 2.9L. That fact together with briann510's example... I think makes it not that far of a reach for big bore SU's on a worked stroker to get near 270 rwhp.[/quote']

My proof is crappy. I'll grant you that, but according to the shitty Gtech test that is all I have to prove my car's power, I made ~240whp. 20% increase from SU's would be 40hp, coincidentally I had estimated it at 200hp prior to adding the triples. My head and cam were not stock, but 20% was about what I got out of it.

But here's some BETTER evidence:

SUs on a 3.1 makes a KILLER street motor. I drove mine that way for years, LOVED it. Mash throttle and GO. At the track it hit a wall at ~5500. A hotter cam pushed the wall up to ~6000, and going to 2" SUs moved it up to maybe 6500, in my case. Going to triples totally eliminated the wall, and peak power is at 6500 now. Still makes good torque at the7000 rpm rev limiter.

On the track, the Sunbelt headwork and cam was next to worthless without the triples. Prior to the head and cam, with 2" SUs and a Schneider grind I got 190 lb-ft and 180hp. After the headwork and prior to 3x2s, the engine still didn't want to pull hard up top at the track, and the midrange was now suffering. No good at all. Installed used triples (had been run on a 3.1 liter in Japan) Thursday, went to the dyno Friday and put down 235 to the wheels at 6500 rpm. At the track that Sat/Sun the car was fundamentally transformed above 5500rpm. WHEEEEEEEE!

Dan said that the you could GET to 6500 rpm with the 2" SU's, but PEAK POWER was at 6500 with the triples. His dyno work does prove that he got 55 whp from adding triples.

I got more about Rebello, stay tuned...

[JMortensen]

Compare this: http://forums.hybridz.org/showthread.php?t=99611

To this: http://forums.hybridz.org/showthread.php?t=87359

Let us know what you make on the rear-wheel dyno, if/when you dyno it. For reference, I know of a 3.1 that did 305 on the Rebello engine dyno and then made 235 rwhp on a dynojet dyno. But of course who knows if the owner/installer had it properly tuned...

Is the Rebello dyno optimistic??? What does this mean for the 270whp SU L engine? You be the judge...

 

EDIT--I don't know if Briann510 saw this post or what but his sig now includes trap speed and vehicle weight which mathematically shows 277.7whp on the calculator I just used. Don't know how dyno hp relates to 1/4 trap speed whether it favors one or the other or they're the same. He did dyno 225 at the wheels though. Makes you wonder if Coffey's car would have a trap speed that showed 310whp or whether it would have shown the same 287 that the dyno showed in his case...

[Guest norm[T12SDSUD]]

Actually Jon, if you notice he said PRIOR to the cam and headwork he got 190 HP . He made the 235HP AFTER the headwork and cam and switch to triples.

He never dynoed the SU's with the headwork and new cam so we don't know how much HP he actually gained,although I don't doubt he made more PEAK HP, what is the TOTAL HP curve comparison below 6000 rpm. I'll bet you dollars to dougnnuts that he made more TOTAL HP below 6000 rpm.

 

That is why I believe the SU's are superior for the street, but inferior for the High Speed Tracks.

 

Later,Norm

[JMortensen]

Still, you got to admit that the change from SU's, even bigger SU's, to triples made one hell of a difference for him "fundamentally transformed above 5500rpm" is a pretty strong statement. And then there is my wife, who was AFRAID of my car after installing the triples, when she used to kick the *** end out getting on the freeway with SU's. First time I took her out I hit it and she turned GREEN and told me to slow down!!! SU's are better in town and at low rpms. No doubt. I thought we were arguing whether triples would produce a large hp gain. I think it's clear that in our two cases they did.

[Guest norm[T12SDSUD]]

Yeah I have never disagreed with the fact that Triples will provide more PEAK HP, however on the street or a slow autocross track with slow turns I believe the SU's would out perform the triples due to their better low rpm characterisitics.

 

I have driven a number of triple carb equipped Z cars on mild cammed L24's and L28's and they were absolute DOGS below 4500 rpm compared to my SU's.

 

And as I said, other than Brian's car, I know of no other stock weight street driven Z with triples running comparable 1/4 mile times to my SU's and my engine is FAR from radical.

 

I think that SU's are the better choice for mildly cammed L6 engines like mine ,but cannot provide adequate fuel and airflow to support a radically cammed 3.1L as evidenced by Dan Baldwin's experience.

[JMortensen]

'']Yeah I have never disagreed with the fact that Triples will provide more PEAK HP, however on the street or a slow autocross track with slow turns I believe the SU's would out perform the triples due to their better low rpm characterisitics.

Kinda true IME. By adding triples I immediately went slower at autox, but at the big track I was WAY faster. In my case that is because I had 3.70 gears, and I was at too low an rpm coming out of slow 2nd gear corners. The national level autoxers use Mikunis, not SUs. But they also have much shorter gears to keep the revs up at slow speeds.

 

Again we're back into street vs race. Not too nice to drive on the freeway at 70 mph doing 4500 or 5000 rpm, but it does prove that the carbs can be made to work at slow speeds. We'll see how mine peforms with the new shorter gears I've got going in... I'm hopeful that I'll have much better results at autox.

[JMortensen]

One more interesting point about the dyno vs ET hp calculation: http://forums.hybridz.org/showthread.php?t=107745 Looks like the JNJ Drag Racing guys were calculating ~750whp in their Z, but when they put it on a dyno they showed 453whp. 300hp difference means that something is fishy. Don't really know what that says for the hp calculation. Maybe the dyno is pessimistic. Maybe the calculation is optimistic. Don't know. But there is a 40% difference in hp measured one way vs the other.

 

The first thing that strikes me is that this could bump Brian, Norm, and myself way down on the hp numbers. I wouldn't expect to make 85% as much power as John Coffey makes with his professionally built stroker running MOTEC and I'm running my home built 2.8L motor which at the time was only 8.3:1 compression. Even if our engines were built exactly the same I should be down 10% by virtue of displacement alone. I also made more hp per liter than Dan Baldwin according to the formulas, and I find that hard to believe. I wouldn't expect Norm to make 235whp with his, and I wondered how Brian could make 278 with moderate compression and a small cam. But then you always hear how you shouldn't compare dyno numbers between different machines on different days, etc, so it really becomes kind of moot really. If you're a drag racer ET and trap speed is what floats your boat, if your a road racer it's whether you can get past the guy in front of you on the straightaway. I'm kinda thinking that HP numbers don't really mean dick. Maybe my butt dyno is the thing I should be concerned with...

[Guest norm[T12SDSUD]]

I have always estimated my HP to be around 230-240 at the flywheel and not at the wheels.

I could be way off but looking at cars with similar power to weight ratios running the same times as mine that's about where I guesstimate my engine to be.

[JMortensen]

OK, and that sounds realistic to me too. I don't know the weight of your car, but I plugged in 2500 (with driver) and your trap speed and the calculator here http://www.race-cars.net/calculators/et_calculator.html shows 240 wheel hp.