anyone have an idea about how much boost is lost through heads/cams?

[ADRENLN]

is there a set amount, or does the amount lost increase as the boost is raised higher?

heres my deal i cant decide between the novi 2000 or a kb. i know everyone here likes the kb, except gearbanger. i thought the paxton would be what i wanted, didnt think it was too much different. then i was reading some old post where TIM from mph said that from his experiance the kb bead centri in every way.

heres my problem. im going to get forged internals and want to run about 12 psi on pump gas. on the paxton im fine, but i dont think the kb 1.7 will be enough. i have heads and cams and will be working on l/t thurs.

so with the 1.7 i could go with the 14psi pully, but only make 9 psi. (dont know what i will lose). anyway i prolly wont get 12 psi from the 14 psi pully that the 1.7 tops out at. so then im thinking 2.2 kb. thing here is the price. on kb site it only says 5,400 not including other parts. with the other parts need, what does it wind up costing? also is the 8 rib set up a must?

i really dont know too much about the kb as i didnt plan on going with it. seems like alot of trouble (2.2) 1.7 would be easy, but im going to be maxing it out and prolly wont see the boost i want. can anyone give me some knowledge on the kb, are they harder to get running on pump fuel at higher boost? i think i will prolly wind up with the novi still.

i just dont want it if a 1.7 kb at 9 psi will beat me novi with 12 psi...you know?

 

[DBMSTNG]

i'd take the NOVI over the KB1.7. but i'd take a KB2.2 or 2.4 over the NOVI. for higher HP, you'll need an 8rib. i'm at the point where it will help me and i'm around 400rwhp. boost loss will depend on how well the new heads/cams flow. you could lose upto 4psi. maybe more. but that's a good thing. if you lose boost, it shows you are making the engine more efficient which means more power. just change the pulley if you want to make up for the lost boost.

 

[jstreet0204]

I think you are looking at it wrong. Don't worry so much about the boost level, since it is not a direct indicator of power. If you are running a the 12psi pulley, but your heads and cams have improved flow to the point where you are only seeing 9psi, then you will be making more power, not less.

 

[300bhp/ton]

is there a set amount, or does the amount lost increase as the boost is raised higher?

heres my deal i cant decide between the novi 2000 or a kb. i know everyone here likes the kb, except gearbanger. i thought the paxton would be what i wanted, didnt think it was too much different. then i was reading some old post where TIM from mph said that from his experiance the kb bead centri in every way.

heres my problem. im going to get forged internals and want to run about 12 psi on pump gas. on the paxton im fine, but i dont think the kb 1.7 will be enough. i have heads and cams and will be working on l/t thurs.

so with the 1.7 i could go with the 14psi pully, but only make 9 psi. (dont know what i will lose). anyway i prolly wont get 12 psi from the 14 psi pully that the 1.7 tops out at. so then im thinking 2.2 kb. thing here is the price. on kb site it only says 5,400 not including other parts. with the other parts need, what does it wind up costing? also is the 8 rib set up a must?

i really dont know too much about the kb as i didnt plan on going with it. seems like alot of trouble (2.2) 1.7 would be easy, but im going to be maxing it out and prolly wont see the boost i want. can anyone give me some knowledge on the kb, are they harder to get running on pump fuel at higher boost? i think i will prolly wind up with the novi still.

i just dont want it if a 1.7 kb at 9 psi will beat me novi with 12 psi...you know?

sorry didn't really understand a lot of that.

heads/cams won't affect boost.

Where are you measuring boost from anyhow, from the outlet on the blower or the intake manifold?

Exhaust mods will affect boost.

Also why won't a KB make 14psi with a 14psi pulley. This is a new one on me. There's plenty of articles about people running 14psi, you'll need to up the octane rating of the fuel to prevent detonation, if you're running stock CR.

I don't see that a bigger blower will have much more chance at producing 14psi and not detonating. The 1.7 is happy producing this power, it's just getting near it's upper limits in rpm. A larger blower will produce the same boost at lower rpms (blower not engine). So there may be slightly less heat build up but not by much.

IMO you should base your decision on power delivery, a centrifugal will be a more highly strung revvy power delivery and will require you to 'ring' the motor out more to get the perofrmance. (similar to a modern straight 4 or v6 engine).

The KB will offer more instant grunt and give you more of an old school big block feel.

A centrifugal blower is not much more efficent than a Twin Screw, so I doubt you'll really be able to produce any significant boost variance.

And remember a twin screw will produce ALL of it's boost from idle to red line. Even if you do get 1-2psi more out of a Centrifugal it will only be over the last 1000-1500rpm or so.

Realistically how much time do you spend with the needle at the red line??

Only you can answer these questions, which should allow you to them make your decision.

BTW how much power are you after (realistically)?

 

[jstreet0204]

heads/cams won't affect boost.

Ported heads and cams will affect boost, as will anything that increases flow after the compressor, causing the compressor to build less backpressure.

 

[300bhp/ton]

Ported heads and cams will affect boost, as will anything that increases flow after the compressor, causing the compressor to build less backpressure.

true, although the performance of the blower won't be altered, just the result.

And I think what I was meaning, is heads/cam shouldn't have any greater affect on a KB than a Centrifugal.

But yes I do see where an issue may lie with p&p heads and cams, with the KB having to run in it's upper performance level.

Anyone know the opertational limit for the 1.7KB

 

[ADRENLN]

thanks guys. well that is exactly what i mean, with the kb the highest pully is the 14. however if i use the 14 pully i wont see 12 psi, which is what i want to see. i will prob. see less boost like 9 psi. so to get me to see 12 psi, id have to get a smaller pully for the kb, but they dont have one over 14. that blower will be maxed out.

i think the 1.7 is not enough for my goals. im not trying to get huge hp out of the car. just want a really fast street car. since im getting a built engine i figure id take advantage of it by using more then 9 psi like most other cars.

anyone know the cost of the 2.2? is it like 7,000 or somthing crazy? if thats the case looks like the novi will have to do.

 

[topgunz_1]

I think 9 psi with really good heads will put out the same power as 12 psi on stock heads. roughly. because the air flows easier the blower isnt as restricted, it can flow the ammount of air easier. same power, lower boost

 

[jstreet0204]

thanks guys. well that is exactly what i mean, with the kb the highest pully is the 14. however if i use the 14 pully i wont see 12 psi, which is what i want to see. i will prob. see less boost like 9 psi. so to get me to see 12 psi, id have to get a smaller pully for the kb, but they dont have one over 14. that blower will be maxed out.

i think the 1.7 is not enough for my goals. im not trying to get huge hp out of the car. just want a really fast street car. since im getting a built engine i figure id take advantage of it by using more then 9 psi like most other cars.

anyone know the cost of the 2.2? is it like 7,000 or somthing crazy? if thats the case looks like the novi will have to do.

I still don't think you quite understand what we are saying. Forget about boost numbers. Flow numbers are what are important. The blower is going to flow X amount of air at a certain rpm. Your heads and cams have only made it easier for that air to get into the cylinders, thus decreasing boost or back pressure. Boost is nothing more than air waiting in the intake to get into the cylinders. Air sitting in the intake doesn't make power. Air in the cylinders does.

Another by-product is lower intake tempatures. Since you are creating less boost to flow the same amount of air, the air has to compress less, which also means it does not heat up as much. Cooler intake temps means less prone to detonation, and more power.

Even if you are not trying to get huge amounts of power out of your car, you will still make a lot with a kb 1.7 and your set up.

 

[Gearbanger 101]

Keep in mind, that flowing through the intercooler on the KB (or a centrifugal for that matter) as a general rule, will eat up about a pound or so of boost pressure, as well. When Kenne Bell rates the boost levels with different pulley sizes, all are rated without the intercooler present. This may work great below 6psi where the cooler isn't present, but when higher boost levels which require the after cooler are present, the numbers tend to get skewed a little.

A centrifugal blower is not much more efficent than a Twin Screw, so I doubt you'll really be able to produce any significant boost variance.

And remember a twin screw will produce ALL of it's boost from idle to red line. Even if you do get 1-2psi more out of a Centrifugal it will only be over the last 1000-1500rpm or so.

Don't forget though....Centrifugal discharge temperatures are far cooler at similar boost levels than Twin Screws are. They may make significantly less airflow at lower blower RPM, but on the flip side, as that blower RPM increases, outlet temps are dramatically lower as boost levels rise and Twin Screw run out of their efficiency range. That's why Centrifugals are always able to run higher boost levels than Positive Displacement blowers without such detrimental effects brought on by heat.

That’s also why I never liked the comparison of boost vs. boost when comparing the two head to head. It always seems to be the argument with the Twin Screw faithfuls, but it in reality that comparison only allows the Twin Screws to hold the advantage for so long. As boost levels rise, so too does the efficiency level of a Centrifugal over a Twin Screw. The Positive Displacement blower is mopping the floor in most cases with the Centi below 6psi, but by 9-10psi, the two are on equal ground and by 13-14psi the Centi has now surpassed the Twin Screw because it’s run beyond its adiabatic efficiency range. If people want to fairly compare the two, then shouldn’t each blower be allowed to run within their targeted efficiency rate, rather than a specific PSI that only suits one of the Chargers?

 

[ADRENLN]

my point is why would i run 9 psi on either blower if i could run 12 and get more power? i know my heads will allow more air to flow in creasing my power at 9 psi over someone who dont have heads at 9 psi.

that is not my problem. problem is that with the 1.7 kb i use the 14 psi pully and only make 9 psi. why would i want 9 psi and x amount of power when i can run 12 psi and get more out of it. that might take a 16 psi pully and they dont make one for the 1.7. you see what i mean.

i didnt even think about loosing another psi through the cooler. well 1.7 is out. novi or 2.2 what the heck is the price of 2.2? no one knows?

i tried to look but it really dont tally everything up.