A naturally aspirated motor, 10:1 compression with aluminum heads and 36* advance.

Or the same 10:1 motor, aluminum heads with 24* advance and 6psi out of a centrifigul supercharger?


I'm wondering if the benefit of the 6psi is worth the 12* reduction in timing, and the obvious drag/power loss of turning the blower.

The efficiency of the blower is about 70%, give or take.

-- Joe

 

Drop the thing to 9:1 and run 12 psi. don't half-*** it. Do the work, then go fast.

 

The 6PSI boost will overcome the reduction in timing. The difference is you will see the gain at upper RPM range and loose some at the bottom end. What octane are these advance numbers at? If this is pump gas you might be able to split the difference with some good fuel.

I do agree with ATILLA the best thing to do is decrease the COMP ratio to fit the SC.

 

Look, once you get used to 6 psi, you're gonna want 9 psi, and on it goes. Horsepower is an addiction. Probably the best one you can do without a girl. You might run forever at 6 psi on a N/A short block, but pistons are cheaper than heads, and forged dished pistons with properly gapped plasma-moly rings will give you the option of upping the boost. (With intercooler or aftercooler)9:1 with aluminum heads and intercooling will allow you to double your power on pump gas. 10:1 N/A with 36 degrees can't begin to compare. If you can afford the blower, then find the money for the pistons and rings.

 

I learned the hard way. Spend the extra money now and don't take short cuts.. You will only want to spend it later to get it done right.

 

And with what ibmtech said there is always this to live by when it comes to cars.

If you can't afford to do it more than once, do it right the first time.

I am looking into a SC for my 305 as well. But way down the road.

 

The blower will be worth more that advancing the timing. If you can save up the extra money and go with the 8-10 psi kit. Vortech makes a good quality product. If you need a sales rep contact for over there PM me.

 

I'm running JE inverse dome pistons $700 with $200 molly rings, H beam rods, forged crank, 4 bolt mains on a balanced setup. My heads a 21* with 55cc chambers.

I ran 16psi on a previous combo. I bought the blower because it was cheap, and I wanted to build a custom singleplane intake for it.


My question wasn't how to build a super fast supercharged setup, I've been there. It was "I'm at 10:1 and I'm not yanking the 5k motor apart to run more boost, should I keep the blower or ebay it".


Intercoolers are neat, but cause too much pressure drop. Had one when I had a thirdgen.. The car made more power with higher temp air and more boost then lower temp cooler boost.

Thanks!

-- Joe

 

Taking the heads off is not an option, just saying.

The moral of the question was, is it worth it to keep the blower. I grabbed the blower cuz it was cheap and I wanted to play around. But I often wonder if I could make as much power N/A with *this* combo.

The combo is a very stout N/A motor. Ton of money into it, all the good parts. Not a blower build, has a 112* cam, etc.

The pistons are inverse dome, -16cc. To get the compression down to 9:1 i'd have to trade my ported 21* heads in for some 64cc heads ($1500), then change the cam to a blower friendly cam ($300), then change the head unit to a S-trim ($1500).. About $3500 to get 8-10 more psi of boost doesn't make sense at all.

So with that said.. 93 octane. Should I ebay the blower and throw more timing at it, or keep the blower?

-- Joe

 

Okay boys and girls, this is an example of doing it wrong. First, not enough info in the initial post. Second, anyone who's not new to adding boost understands that the intercooler is worth the hassle of having to add a bit more boost to compensate, because it'll let you run more PSI in the intake manifold with cool air than with hot air. In other words, if you have 10 psi coming out of the blower, at 250 degrees F, and you add an intercooler, you're now gonna need 11-12 PSI coming out of the blower to have 10 psi in the intake manifold, but now the air is 150 degrees. Because of this, you can now up the boost until you have 12-13 psi in the intake manifold. This guy didn't compensate. Lastly, don't build a 10:1 engine if you own a supercharger. This guy could do what he asked. Or he could order a custom cam to kill the dynamic compression, and have one hellacious top end. Supposedly, his bottom end is up to turning 7000+ rpm. But then he needs a loose converter, and the $1200 he just spent on cam and converter woulda been better spent selling his milled heads and getting a new pair of 75cc AFR heads. Spend a little to get it right, or sell the blower and go slow. Watch this guy start hatin' for what I just typed. The truth does tend to make guys angry.

 

You hit the nail on the head. My current build uses AFR 75cc heads but the intake temps were still HOT HOT HOT.. I am running the V-3 Si-Trim and found that by adding a FMIC, I noticed a major power increase. I have pics posted on how I got the FMIC installed..

http://www.cardomain.com/ride/2423655/4

 

sweet! the intercooler just visible through the foglight holes. Makes me want an intercooler even though I'm not boostin'.

 

Keep the blower and throw a little more timing at it. I suspect it can tolerate some more advance.

1-2 psi boost should be enough to overcome the compressor drag. The extra boost should result in more power compared to NA.

We know intercooling isn't really an option since the resulting increase in flow rate corresponding to the increased density will just put you further to the right on the compressor map, not to mention the pressure drop though the IC.

Intercooling is only really effective when the supercharger has excess capacity and can maintain a sufficient pressure ratio at the increased flow rate.

Here's an interesting NACA report on the effects of aftercooling considering supercharger capacity:

http://naca.larc.nasa.gov/search.jsp...vestDate%257c1

Here's another interesting report which covers input drive power and compressor maps of some popular centrifugals:

http://www.superchargersonline.com/i...1sc_report.pdf

 

Loose converter? it's a 6 speed car.

I experimented with intercoolers years ago. I don't feel the need to get knee deep into tech. I've been there, done that. I also ran alky injection too, which saw a better temp drop across the board with zero pressure drop. I don't feel the need to get into all of that because it has no bearing on the conversation at hand.

I don't know what a hatin' is. But I do know I've run a lot of combos over the last 15 years. My question, to the senior guys was very simple.

On a 10:1 motor, what makes more power 12* more advance, or 6psi of boost. End of story. Sorry I asked.

-- Joe

-- Joe

 

I wonder. I built this shortblock for a blower project on another car, but when I decided to use it in the corvette I milled up some heads for a 10:1 out of the box, which In theory is probably close to my 'normal' blower build which is a 9:1 iron head. The aluminum heads take a lot of heat (and power) out of the chambers, and in theory so would a little more advance but if it detonates a compressed charge it tends to break things. Then again the pistons should handle it. Don't know if the valve seats will.


It's a little boggy off the line. I don't want to regear it again because with this tire size it should be dead nuts @ around 125 mph at redline in 4th gear.

I tried leaning it out a hair for the tip in, but rather than curing the bog (thought it might be a rich bog) it causes a lean pop so my conclusion is the cam is too big for 3.54:1 (224/230 @ .050) or the compressor drags too much down low...


You and I know that. Mr. expert who doesn't have a supercharged car (post 12) wants one for his n/a stocker.

I'm only seeing mid 150s F for temps out of the blower. Even my S-trim didn't go over 171.9 degrees F according to my logs from 2004.





Good stuff. I'll check it out.

-- Joe

 

We had a similar discussion not too long ago on the Turbo Buick boards. I would go with the 10:1 motor w/supercharger, but with one stipulation though, run the smallest pulley available, and install a wastegate (set at 6-psi) in the inlet tubing. I met up with a guy over at e-town not too long ago who got the idea from a mustang article written a few years ago, Click Here. I had my doubts at first, but no more though, as the power under the curve was just too freaking much @ only 7-psi. I'm honestly flirting with the idea myself now....;

 

That's an interesting idea.. If I had a bigger head unit or upgraded impeller.. I have wastegate control too on my '749 ECM.. I think the powerdyne would explode at higher RPM's though..

It is a neat idea though. If I could build like 6psi steady from 2000 RPM up .. I wonder.

-- Joe

 

Does that put excess wear on the super charger though?

 

Yes, It would eat a bearing. The concept is solid for different blowers, that can spin higher and have a higher overall efficiency. I can run a slightly smaller pulley but I'd be on the edge of bearing failure and efficiency dropping off.

Say the theoretical max the car could take was 10psi, and you take a T trim blower that would make around 20psi at 6k. You put a very small pulley on it so it makes 10psi at around 3k, and 10psi at 6k with waste..

It's a wonderful idea, but my head unit doesn't have the airflow to pull off such a trick. When I first got it I wondered if at all it pushed enough airflow to feed an already 400hp car with good heads, but as I discussed with Tequilaboy yesterday the boost actually comes in a little quicker on this motor than on my S-trim with the firechicken if I compare datamaster graphs.

Though the S-trim made more overall boost (14 or so psi @ 6k), the powerdyne seems to bring what it has in quicker. (3psi at 3k, vs 2.3 psi at 3k on the s-trim).

-- Joe

-- Joe

 

You could and it's called a turbo.

As far as your original question, the supercharger should make more power.

 

Turbos are neat. Turbos in vettes are big money though. Lot of clearance issues, heat problems, etc..

Turbos also have very hot outlet temps, which bring us back to the intercooler, which routing on a vette is another nightmare.

Thanks!

-- Joe

 

Joe
I think STS has a rear mount turbo kit for the C4 / LT1 now. They claim you do not need the inercooler because the piping to the rear of the car acts as a intercooler. I have not seen one on a C4 however I have seen a few on C5's and the ones I seen made some VERY impressive dyno numbers on a stock car. If the C4 kit is anything like the C5 kit there is not much if any cutting on the car and basically a bolt on deal. You are correct that it is NOT a cheap option.

 

STS is great. I like how everyone (well not everyone, but Z31 guys do) doubts their kits, then when they bring a new one out, its better than previous versions. Its awesome.

I remember when STS started they were getting boost around 3,000-3,500rpm and now I have heard/seen boost spool as low as 2,000rpm on some of their kits.

Best part, their kits always work with stock cars

Thats all.

 

It's neat. Lots of plumbing though.

I like blower. Pretty direct and simple. If I had more engine bay room I'd do a twin turbo. A rear mount has a cool factor, but I dont have that much energy. As it is I'd sell the car for the right offer.

-- Joe