yeah...turbodiesels which are bit different.


but the vw 1.4 (enter acronym that i can't remember here) is turboed AND supercharged.


and there is a big difference in a factory equipped turbocharged car, and an aftermarket turbo. one will be fairly seemless, the other not so much.

 

Yeah. I looked up roots type and screw type superchargers the other day. Holy cow they are large. No way the Rotrex is as parasitic as those. I'd think that is is probably similar to turbo losses.

 

The reason this is true is because boost pressure is only a small protion of the equation.

Many people merely look at PSI and disregard the other really important part: CFM!

5 psi flowing 200CFM is going to make more power than 5psi with only 125CFM, everything else being equal.

For example: My Eagle Talon turbo I used to own had a 14b turbo OEM. I ran it, with a few other mods, at 20psi. The car ran a 13.4 sec 1/4 mile. Much later I ran the very same 20psi, and the car ran a 11.2 sec 1/4 mile. The difference? I had a GT3076R DBB turbo on it the second time. The CFM was massively different as well as the efficiency range.

At redline, the 14b was flowing about 370CFM at 20psi and was running at about 60% efficiency. The modified GT3076R I had was flowing more than 625CFM at 20psi and was running close to 80% efficiency.

The 14b at 20psi was way beyond it's efficiency range. Past a certain point, you get diminishing returns from your investment. I could have turned it up to 23psi, but I would have run slower because the turbo would have been blowing really super hot air. The hotter the air, the more detonation, the less timing you can run, the less power you make.

Comparing a 5psi turbo to a 5psi s/c is really comparing apples to elephants. Two very different things, that honestly, you can't really compare, as far as power-wise.

 

True, but unless you massively change something in the engine you're not going to get 60% more flow at 5 psi.

An increase in flow requires an increase in PSI or better flowing components.

An increase in PSI does not guarantee an appreciable increase of flow (your example above is a good one).

 

I'm not talking about flow through the engine. I'm talking about flow in/out of the turbo or supercharger.

There are turbos/sc's that will flow 125CFM at 5psi and some that flow 200CFM at 5psi, at a given RPM. It's completely independent of what the engine can or can't flow.

Now if you were talking about an engine, say maybe flow through a head, then yes increasing CFM by 60% through a head would take a heap of work.

My stock 4G63 head flowed about 240CFM at a .600 lift I think. After the stage 4 port/polishing job I got, it flowed over 275CFM, about a 15% increase in flowrate.

 

Look, I don't know what tangent you are going off on, but the original question was: "How can turbo "x" make more power at about the same boost pressure as supercharger "y"?"

What the boost pressure is (as far as this question is concerned), is irrelevant. What I was trying to explain was that you have to take into consideration of CFM flow as well as pressure when dealing with forced induction. The fact they were both at about 5psi is irrelevant.

For any turbo or supercharger, you have different flow rates dependant on pressure and RPM.

Just because two turbos or two supercahgers or one of each, are set at 5psi, or 10psi, or 50psi, doesn't mean they will make exactly the same power. If they have different CFM rates, they will make different power.

And I am talking about the CFM output of the turbo or supercharger. Not the CFM of the engine( or flow-rate of the head).

 

one thing i'd like to point out is were talking about a centrifugal supercharger which basically is the same style compressor as a turbo charger but has a planetary rotating assembly to convert the engine rotating speed to a much higher compressor impeller speed. so theoretically you get the worst of both worlds. you get lag accompanied with parasitic loss. granted the rotrex rotating assembly is probably the best around right now. so boost is going to be linear with engine speed. peak boost isn't going to be realized untill redline. this is nice if you want consistant power delivery.

you have to remember positive manifold pressure (aka boost) is a sign of restriction. i'm willing to bet if you pullied the supercharger at 5psi and you ran a larger primary header(say 1.75") and 2.5" exhaust you would loose "boost" (less backpressure) but make more power at less psi.

now a turbocharger is a different animal. it uses expanding gasses to spin the turbine which in turn spins the compressor thus making "boost". so to spool up the turbo you need a load. that is why it will spool faster in higher gears (3rd, 4th, 5th) as apposed to 1st or 2nd. running a smaller turbo will spool faster due to smaller volume to fill and a lighter rotating assembly but the byproduct is exhaust backpressure. so 5 psi on a small turbo will be far different than 5psi on a larger turbo (as stated above). "boost is controlled by a mechanical wastegate which opens at a set pressure. now lets say you have that small turbocharger with stock exhaust. lets say at 5psi your flowing 200cfm(using theoretical numbers just to gain a understanding) and have 20psi of exhaust backpressure. now lets say you open the exhaust from the turbo back to 2.5" now lets say you now only have 10psi of exhaust back pressure. well now your probably flow 240+cfm but since the wastegate is mechanical it still only shows that same 5psi but your now moving more volume of air, thus making more power.

a simple way to look at it is to just think of the engine as an airpump. the more air you can get through it(while maintaining a correct fuel mixture) the more power it will make. more air + more fuel=more power period! granted there are millions of ways of filling in that equation but you get the idea. and we won't throw timing into the mix yet.

 

I brought that point up in the main KWSC thread, if the kit would reach 5 PSI with header + exhaust, but there was no reply yet.

 

it's going to depend alot on what size exhaust and which header you'll be running. another thing which will play a role is your elevation and temprature. the lower your density alititude (DA) is the lower your boost will be. centrifugal compressors operate at a certain pressure ratio (PR) at a givin impeller speed (which is determined by the engine speed and pully sizes) engine volumetric efficency (VE) also plays a role.

one thing I've seen done on centrifugal superchargers which I feel works great is to over drive them (basically pully them for a high boost level) then run a pop off valve. which is basically nothing more than a valve with a adjustable spring in it(similar to a blow off valve, but doesnt have a vacume line) then say your pullied for 15psi at 7000rpms you'll set your pop off valve at say 5psi. then you'll basically get max boost at a lower rpm and keep it to redline. you could theoretically tune your tq curve to your liking by overdriving it to make a desired psi by a certain rpm then control it with the pop off valve.

CAUTION: if you do decide to run a pop off valve and overdrive the compressor, just know your genrating more heat so intercooling would be a wise investment. and you will need some sort of tuning becuase your going to lower your peak tq rpm which will cause detonation and timing will need to be retarded in that area.

 

doesnt the spring in the wastegate determine bosst pressure, not the blow off valve?? haha.

 

on a turbocharger yes. but I was speaking of ways of maximizing a centrifugal setup. same concept as a wastegate but called pop off valves for superchargers.

 

[quote=underdog;344462]one thing i'd like to point out is were talking about a centrifugal supercharger which basically is the same style compressor as a turbo charger but has a planetary rotating assembly to convert the engine rotating speed to a much higher compressor impeller speed. so theoretically you get the worst of both worlds. you get lag accompanied with parasitic loss. granted the rotrex rotating assembly is probably the best around right now. so boost is going to be linear with engine speed. peak boost isn't going to be realized untill redline. this is nice if you want consistant power delivery.

quote]


so is it theoretics or is it actually laggy? because i've never heard of anyone complaining of lag or loss.

 

[quote=eldaino;344757]depends on how you want to look at it. boost is exponential with engine speed and according to rotrex's site it is a 90% efficient rotating assembly. so again in theory it takes 10% of the power from the engine to rotate it. this will also depend on the pullied ratio.




this sort of helps illustrate the different boost curves. ignore the areocharger and positive displacement plots. just compare the blue and black lines. with the centrifugal you don't see peak boost untill max rpm. so yes you can call it lag, or you could look at it as constant controled power delivery.

you can see by the illustration with a conventional turbo there is going to be a massive surge of power between 2500rpms and 4500rpms (your boost curve will almost always define your tq curve up untill peak tq, which is roughly at peak boost.) this can be a bad thing when your racing, since your going to have to control the spike of tq which requires alot of traction and throttle modulation. granted this is a generic illustration. with the advance in technology, ball bearing turbochargers and more areodynamic wheel profiles and electronic boost controllers can help tailor your boost curve to your needs.

 

You are both right.

The wastegate (not the Blow Off Valve) does control the boost level on a turbo setup.

You have the BOV to prevent the turbo from slowing suddenly during gear changes when the TB shuts quickly.

But a pop-off valve for a s/c is very similar to a BOV for a turbo. The are both on the pressure side of the charger and they both have spring actuated valves.

In a BOV (turbo) application a reference/vacuum line exerts pressure to keep the valve closed under boost, and "sucks" it open (along with aid from the spring) under vacuum.

In the pop-off valve (s/c) application there is no vacuum line attached, so when boost pressure reaches and exceeds the spring pressure, it opens to vent boost.

 

What setup would be better for a reliable daily driven car?

It seems like the KWSC would be, but are there actually any proven risks in going turbo over sc?

for example: can you go on a 8hr road trip with a TC Fit without the fear of overheating?

What are the actual benefits of T1R turbo over KWSC and vice versa?

I think this is what I am looking for from this thread.. which is better and why. Risks involved with each kit, and benefits.

I'm going to be getting either kit very soon... I am still waiting on the hondata/highboost numbers before I make my final decision.. but I want to know if I am wasting my time waiting for it since the T1R kit is already available.

 

yeefit: i still say go with the KWSC.


all the turbo set ups out there right now throw a cel, at least the kw has been proven that it wont, when installed properly.

its linear and it runs A TON cooler than pretty much ANY turbo set up that will EVER be out for our cars. and that is proven, not just speculation. turbos will be peaky, albeit fun when boost hits, but the kwsc is going to give you the feel of a bigger engine, which is going to be more seamless in power delivery and thus better for what seems to be your needs.

 

the KW fit wont throw a cel with the base kit no injectors that has been proven real world. as for injector upgrade no dice. not without hondata but that has not been proven real world yet. comparing the base kit and the t1r turbo as is without a re-tune they are pretty close to the same price. you will gain a shitload more power with the turbo. i don't know what specific cel's have been thrown with the turbo and noone else has provided that info on this thread that i can see. so the cel could be tune related or setup related who knows.

the 10psi, hondata etc has not been released yet so who knows what the end result will be. i would think that it would make a drastic difference in performance.

side note: dynos can be made to say whatever you want. butt dyno is the real payoff imo. a friend with the base kit M/T with catback exhaust dyno'd 2 runs. 1st was 111 and the 2nd was 114.9hp. boost didn't hit 5psi until 6000+ rpm's

 

butt dynos ftw. and both kits will provide you with it.

 

ok so the check engine lights that have been going on with the T1R kit, i just got a cel today and it was the barometric pressure circuit. i called ben and asked him about it and he said to ignore it for now because he is working on an adapter for the map sensor. so the cel is really a non issue.

 

how's your kit running otherwise. any dyno results?