The Stillen SC kit is pretty good, in my opinion, but I never have liked the way the intake is routed right over the exhaust manifold and over the radiator, where it can pick up a lot of heat. I have seen steady state temperatures of up to 150 F in the air going into the throttle body, and boosted temperatures as high as 185 F.

This weekend I spent some time addressing the problem.

 

 

 

haha.. That looks pretty slick. Have you noticed any loss in PSI, since the pipe is longer?

VERY cool, IMO.

Thanks for sharing.

 

Since I already had a left over prcai, I just reinstalled it and connected the driver's side piping to it.

Results?

Yesterday afternoon I drove around in the 95 degree weather and didn't see temperatures above 125 F, and that was sitting at a stop light where incoming air is minimal and has time to be heated up by the blower. Once I got rolling again the temperature would drop quickly to about 110 F. The drop in temperature was significantly faster than what I used to see before.

I did a boosted run to 7000 rpm, which I datalogged. The log showed a maf voltage of 4.39V, the highest I have ever recorded, at 12 psi of boost. The intake air temp got up to 160 F, a good 25 degrees lower than it would have boosting on a hot day.

Am I happy? Yes, but not completely. The wonderful howl that the stock piping gives at about 2500-3000 rpm is gone. I loved that howl because it sounded just like an F4 Phantom jet at low turbine speed. If you have lived near an air base that had Phantoms, you'll know what I mean.

Not only that, but I get a fairly loud chuffing noise in place of the howl. The chuffing noise is due to air oscillating back and forth in the piping. The longer piping distance allows for greater dynamic oscillations in the air flow. At low throttle, such as cruising at 2500 rpm, the blower is trying to pump much more air than the engine is taking in. There must be an acoustical resonance that produces the oscillations, and it results in air alternately being forced into the intake piping and then forced back out again, resulting in the chuffing noise. It was very apparent what was happening when I had the filter off the blower and could feel the oscillatory back flow from the blower inlet. I'm not sure how to rectify this. Maybe a larger blow off valve will dampen the oscillations. An intercooler may also dampen the flow sufficiently.

 

Boost loss was maybe on the order of tenths of a psi. I still hit 12 psi at 7000 rpm. I think I have recorded a maximum of 12.2 psi previously, but that was on a colder day, too.

 

WOW, Great idea!
Props

 

Where did you relocate your blow off to ??

-matt

 

Nice thinking.

What do you use to monitor intake temp? I'd like to put one before/after my IC

 

I don't show it, but eventually I put it in the short, straight section in the passenger side fenderwell.

 

damnit Stephen....u just have to out do us all huh? prop to ya...are u gonna put an intercooler in between there too?

 

I've got the Autometer two-channel intake air temp set. It measures up to 300 F, if I recall correctly. I have one thermocouple at the blower inlet and the other right before the throttle body.

 

One of the reasons I did this was to prepare for an eventual fmic setup if/when I convert to a turbo setup.

I'm not in any hurry to mount an intercooler, but if I find a good one for cheap I'll do it sooner rather than later. I'd like to see how much lower than 160 F I can get the intake air without a serious boost loss.

 

I saw the post under mine, that's awesome


and is it just the noise? or does the car buck at all?

Is the noise that bad?

 

I see a front mount IC in your future! Nice!

 

The car runs as smooth as ever.

The noise is annoying and somewhat embarrassing. It isn't that loud, but it sounds like something weird is wrong with the car. At higher rpm it sounds kind of like a breathy rattlesnake.

My exhaust is really quiet, though, maybe it's time to get a 3" exhaust to mask it.

 

What you're describing is compressor surge. I didn't realize a SC could have this, but I don't see why not.

Basically, the back pressure after the compressor is exceeding the compressors' flow at that point, which causes the air to flow backwards into the compressor causing the wheels' blades to loose "grip" and slip on the air. This causes turbulance and the compressor flow to decrease. The decrease drops discharge pressure allowing the compressor to push air again until it reaches the "surge point" again.

I would think with your PF TB and matched IM is not contributing to the problem(usual suspect), however the increased backpressure from the addtional piping/bends is.

You might want to follow Corky Bells' advice(I know you have his book) and rig up a few pressure gauges to see what's the restriction that needs to be improved.

 

Yes, you're right. I don't know why I didn't come right out and call it that. If you look at the V1 and V2 compressor maps on the Vortech website, you will see that SC'ed Maximas are operating to the left of the efficiency island and close to the surge line even at WOT. The situation gets worse with smaller pullies. At low throttle and mid to high rpm we are definitely crossing over into the surge regime. That's why I think a bov that allows more air to escape when manifold pressure is negative (i.e. vacuum) may be the ticket. I just happen to have one, but I have to figure out where to put it. It's HUGE.

 

That will most likely solve it.

If you wouldn't be considering a FMIC or incase the BOV doesn't work, I'd have chose another route to your original dilema...lowering intake temps. First, I would have sent the discharge pipe to SwainTech and had them ceramic coat the inside and outside of the pipe. Then I'd have used some kind of heat shield like Thermo Tec to wrap the pipe and header.

I *THINK* you could have achieved that 20-degree or so drop in temps without the added piping restriction and lag. IMO, although it may only be noticeable on a dyno, you've added lag to the system by increasing the internal volume of the intake tract that must be pressurized before boost can enter the IM. I have no idea how much, but shorter piping has to be better.

 

I didn't add any restrictions, just extra length. Okay, I guess that counts as restriction, the effect is the same, but I'm using 3" pipe, so pressure drop is minimal. The main reason I cut through the sheet metal is to minimize extra turns, which is where you really lose pressure (aside from an intercooler). I feel I was successful in that regard as I can detect only a .2 psi drop in pressure from what I've measured before. There has to be increased lag, but I can't really tell from driving.

I backed off on the bov preload spring last night, which helped a lot in reducing the chuffing noise. Now it only does it when decelerating with the throttle closed.

I guess I am doing this because I am sneaking up to a turbo. The immediate goal was to lower intake temps (and I'm very pleased at how well this has worked), but after all is said and done, subconsciously I'm wanting that fmic and turbo.

 

Good...I'd love to see what you could do with a turbo, since you've eeked out pretty much everything that SC can give.

What effect does backing off the BOV preload spring have under boost? None?

 

If the BOV spring isn't tight enough there can be boost loss.

 

Thanks......

 

edit: Not sure what I was really thinking in the original post but it seems as though if you go too tight there might not be enough vacuum to open the valve. I e-mailed TurboXS to see if they agree but I'm almost positive that would be the case. You would definitely have a bad idle and lose some boost if the spring is too loose though. The boost would overpower the spring's tension and allow it to open a little.

 

I know maxioverdose and others that wanted faster boost from a smaller pulley withOUT too much peak boost would loosen the BOV to bleed off boost.

I'm just not sure whether the preload spring is what they are "loosening" vs. Stephen Max.

 

I'm not sure what bov he's using nor what style but in my TurboXS RFL there is only one spring that can be adjusted. I would think most of the others would be similar (except for maybe the HKS SSQV) but I could be wrong.

Letting it bleed boost should allow it to spool faster but it would probably decrease maximum boost and probably make it idle weird or run a bit rich since metered air is being released.

 

I have the Blitz DD bov. The preload spring is mainly used to determine how much and when the bov opens under vacuum. The more preload you use, the sooner the bov shuts as you open the throttle, and you can begin to build up boost with the throttle less than wide open. Used this way it can increase throttle response.

At WOT, the vacuum line delivers boost pressure to the back side of the plunger to help keep the bov closed (along with the spring force) when boosting. If you have zero boost loss between the charge pipe where the bov is situated and the intake manifold, then the pressure on both sides of the plunger is equalized and the spring keeps the bov shut. In actuality there is always at least a little bit of difference between the pressure in the charge pipe and the pressure in the intake manifold, so there can be enough of a pressure differential acting on the plunger to work against the spring and eventually open it, resulting in boost loss. This also depends on how stiff the spring is.

To answer your original question, I don't know if I loosened it to the point where I will leak boost. I suspect so. My Vortech Mondo bov will rectify that situation and still allow sufficient release of air at partial throttle driving. I think. If not, then I'm going to see if a fmic will provide sufficient baffling to suppress air oscillation under surge conditions.

 

Auuugh...that makes sense.

Maxidose was bleeding off peak pressure through the BOV at higher RPM by increasing the difference in pressure to the spring causing the spring to be overpowered and open. Gotcha...thanks.

 

I don't think he has! Call Me crazy but the 3psi I lost with the intercooler was significant But my intake temp (good guess) is close to ambient if not at it and with 6-7 psi boost although I do notice some lag as compared with the 3.33 before the fmic was installed. So my next step I think is to upgrade to better trim blower- the T Trim and possibly the v-1 gearing also. Of course after I can get some type of good feeling (from you guys) on ecu tuning options <please pm your thoughts on ecu tuning and what is best I am planning 500 or greater cc injectors as 370cc is too small>.

 

PLEASE prove me wrong.

I think eManage is your best route.

 

PLEASE prove me wrong.

I think eManage is your best route.

 

prove you wrong on what?? that he has exhausted the s/c route?

 

Some intresting reading!!!!
http://www.autospeed.com/cms/article.html?&A=0629

 

very interesting
I need to study this for a while.

 

Yeah, that you can figure out how to squeeze out more power.

Just hoping...

 

I know that the hks makes terrible surge for the blower. I have the blitz now and have it tightend down to where it releases at 3k and gives a faint hum when shifting at cruising speeds. Shifting from 1st to 2nd at wot creates a healthy shutter sound. I messed with the bov constantly untill I felt it was perfect. I feel its just right and has smooth drivability. Too tight seems to create a bogging feel .

 

Well, I know I can get good gains by improving my exhaust. And there is always nitrous.

 

I think you know what I mean...I'm not interested in max power....just efficiency and safety.

You've MAXimized the airflow by minimizing the restriction and pushed the SC to the relatively safe max IMO.

I'm sure there is a little more, but I think you've done about everything reasonable except headers/catback exhaust. Cams/nitrous is a different level of complexity.

 

I bet with the 3 inch exhaust your car would OPEN up on the top like you would not believe.