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Losing Boost... 

 

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 Post subject: Losing Boost...
Posted: Tue Sep 27, 2005 6:04 am 
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I've finally got my car all done, and it has been being tuned for the last week.
The problem i have is that the Wolf ECU is only showing that i am getting 4 PSI, althought i have the 8 PSI pulley. The guy that is tuning my car, has told me this, and Justin from CAPA has suggested that i might be losing 4 PSI or more through the Intercooler...
Would you think this sounds like it could be the problem.
Its not an axpensive cooler, but i thought i may have lost a lot less than 2 PSI max out of it.
Do you think its worth just bypassing the cooler, and going straight to the throttlebody, or driving it around for a bit, with only 4 PSI and trying to find a better cooler (if that is the problem).

Dave
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Posted: Tue Sep 27, 2005 6:17 am 
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If it is easy to bypass the cooler I would try that first and see what you are getting. I assume you have checked all your connections etc for leaks. Another thing to check is the BOV, normally they don't leak at that low boost but it is possible. Also, it greatly depends on what rpm they rev it to, the vortechs love revs and probably need about 6000rpm to make full boost.

What size puley is it, 3.33"? The same pulley will produce different boost levels on different engines but your engine is otherwise stock isn't it?
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 Post subject: Re: Losing Boost...
Posted: Tue Sep 27, 2005 6:20 am 
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EL XR8 wrote:
Do you think its worth just bypassing the cooler, and going straight to the throttlebody, or driving it around for a bit, with only 4 PSI and trying to find a better cooler (if that is the problem).



Dave,

I think it's worth trying this to determine if the intercooler is your problem or not. Few other suggestions...

Got a mechanical boost gauge? i.e. it would be worth making sure the value being reported by wolf is correct. A leak in the vac line to the MAP sensor may throw out the readings.

Make sure the belt is gripping. It's important to get the correct balance between 'not too loose' to ensure strong grip and 'not too tight' as this places uneccesary strain on the blower's input bearing and also the idler/tensioner pulleys. As a rough guide, my belt is about the same tension as the engine accessory belt (i.e. water pump, p/s pump, air con etc). Some belt grip spray may help in this regard, but be warned - the belts are disgusting to work with once they've had this stuff on em.

Make sure everything is on tight and is not leaking. This includes the input plumbing to the back of the blower as i imagine the PCV vents into this line...


Soooo.... how is it at 4psi?? Glad to see she's up and running. Justin is a good help, too. Top bloke.

If it is the cooler... get a smaller pulley and ramp the boost up. Can get em on ebay IIRC or from the vortech site, capa may have a small one but bring your wallet, lol.

 

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 Post subject: Re: Losing Boost...
Posted: Tue Sep 27, 2005 6:24 am 
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4.9 EF Futura wrote:
Make sure the belt is gripping. It's important to get the correct balance between 'not too loose' to ensure strong grip and 'not too tight' as this places uneccesary strain on the blower's input bearing and also the idler/tensioner pulleys. As a rough guide, my belt is about the same tension as the engine accessory belt (i.e. water pump, p/s pump, air con etc). Some belt grip spray may help in this regard, but be warned - the belts are disgusting to work with once they've had this stuff on em.


Yeah thats another big thing, the belts need to be BLOODY tight, especially if you are running a 6rib pulley. I also found the belts stretched fairly quickly so its worth a check.

But yeah if all else fails a nice small pulley will solve any boost issues :D
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Posted: Tue Sep 27, 2005 7:00 am 
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I actually haven't driven it yet Martin, i pick it up tomorrow. :D
I am running a 3.15" Pulley at the moment, which Justin said should show 8-9PSI, but thinks the cooler is losing all the 4PSI i need!
I also have a 2.75" Pulley sitting at home right now, which should bring about 12PSI. But he said: "it might slip or something similar"... I didn't understand that statement from Justin
Also, its an 8 rib pulley, if that makes any difference from a 6 rib????
THe guy tuning it said its running 185rwkw at 4PSI, so should see 220-230 at 8PSI. So although i'm looking forward to picking it up i'm still a little disappointed.
I was going to ask the guy who's tuning it to see if he could fit an intake pipe(hose), straight from the blower to the Throttlebody. Just to see if that works.
Otherwise i will have to test these things out myself over the next week. The good thing is that the Wolf has the Hand Controller so i can see exactly whats going on if i change things.
*My engine is stock, except for a s**t exhaust and Genie's.

I personally think i will just drive it around for a week, until i can try and solve these problems myself, or at least narrow them down, then get it back on the dyno to tune it if i put the smaller pulley, etc on.
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Posted: Tue Sep 27, 2005 7:36 am 
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A 4psi loss is unusual... Ive seen this on old school intercoolers, like the old supra and silvia things, but not on bar and plate coolers of decent size. What size is your coolers core? and what size pipes?
If its similar to mine it should only drop a psi or two... pressure drop means nothing to me as I can just turn the boost up a bit to compensate, pity its not the same on blowers.

The Wolf should be very accurate at displaying pressure, mine is exactly the same as on the boost guage... you should get one of these, autometers are cheap and accurate.

Just check all your vac lines and intercooler hose/clamps, you might be loosing a psi somewhere there and combined with the cooler and pipe length, can add up.
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Posted: Tue Sep 27, 2005 7:37 am 
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mmmm I was told that the 3.15 pulley should easily make 12psi, mine made about 8psi with that pulley and thats on a modified engine. I thought I would see more boost than that (haven't seen what it pulls now with the new piping etc), so you should see at least 10psi IMO.
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Posted: Tue Sep 27, 2005 7:44 am 
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EDXR8 wrote:
mmmm I was told that the 3.15 pulley should easily make 12psi, mine made about 8psi with that pulley and thats on a modified engine. I thought I would see more boost than that (haven't seen what it pulls now with the new piping etc), so you should see at least 10psi IMO.


Does this mean you lost 4psi through your intercooler too?
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Posted: Tue Sep 27, 2005 7:46 am 
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Ok I just checked and these are the typical boost levels you should see:

3.47" - 6-8psi
3.33" - 6-9psi
3.12" - 10-12psi
2.95" - 12-13psi
2.75" - 14-15psi

These figures are also using a 6.8" crank pulley, CAPA says theirs is a 7.2" so should make even more boost.

So if yours is a 3.15" pulley then there is a problem, the IC can't be responsible for a 6-8psi drop.

CHEF wrote:
Does this mean you lost 4psi through your intercooler too?


No I am not running IC with mine. I assume the lowish boost I am seeing is more to do with engine mods. Still got tuning to do before I get it up on full boost on this setup but its nothing the next size pulley won't fix.

EL XR8 wrote:
I also have a 2.75" Pulley sitting at home right now, which should bring about 12PSI. But he said: "it might slip or something similar"


Yeah with smaller pulleys the belt has less surface area to grip therefore slip more. Also 2.75" is too much for a stock bottom end, if you do fit it make sure you have an ultra safe tune but even then I wouldn't think it would last all that long.
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Posted: Tue Sep 27, 2005 8:33 am 
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I've got a mech. boost gauge, but i still have to source the exact size of tubing, cause the one they give you isn't anywhere near long enough.
I have a 'normal' bar and plate cooler, although a cheaper one.
Its about 70-75mm Core size, and the piping should be 2.5" which is the same as the blower outlet or about 5mm smaller.

I get it back myself to look at and drive for the first time tomorrow, so i will have to have a look myself when i get some time, and figure this all out.
I think my Crank Pully was 175mm, so 7" in the old scale.

It s**t me, the guy who is tuning it, knows his s**t, but even this is stumping him. Plus i guess he is busy, so....
I think its a job for meon the weekend!

Do you reckon 185rwkw @ 4PSI is pretty good for a stock motor?
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Posted: Tue Sep 27, 2005 8:43 am 
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EL XR8 wrote:
Do you reckon 185rwkw @ 4PSI is pretty good for a stock motor?


IMO 185rwkw @ 4psi is extremly good, I would be expecting that sort of power from around 6-8psi which is what the Powerdyne guys get. It sort of makes me think you may have a bit more than 4psi, either that or the dyno reading is on the high side.
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Posted: Tue Sep 27, 2005 9:38 am 
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Yeah, seems high to me, but if thats an accurate power figure then your doing very well. But on a 5lt, you would expect 230wkws on 10psi atleast, so 185 from 4psi sounds right to me...
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Posted: Tue Sep 27, 2005 9:23 pm 
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EL XR8 wrote:
Do you reckon 185rwkw @ 4PSI is pretty good for a stock motor?


I guarantee that'll put a smile on your dial. 185kw is a great figure, these things usually take time to get 'perfect' so you're off to a good start.

The difference with the 8 rib (compared to the 6 rib setup on my powerdyne) is increased surface contact between belt and pulley - meaning less chance of belt slippage if/when you decide to go to a smaller pulley. Smaller pulleys are harder for the belt to gip and the extra boost created means more resistance from the blower pulley. 8PK belts will cost a bit more (by the way, if you have CBC bearings in your state, its an awesome place to get belts for 1/2 what CAPA charge).

Sounds like you know what to do to sus it out. Hopefully not too much hassle running a pipe straight from the blower to the TB. If this sees higher boost levels then obviously the IC is costing you boost or there is a leak somewhere in the IC plumbing.

Unfortunately leaks usually only rear their head under boost... so you need to be on a dyno to examine the engine under power... but i'd be suprised if your tuner hadnt already looked for them.

Get that boost gauge hooked up ASAP. Sprint auto or repco should be able to sell you any length of vac hose you require for a few bucks.

Good luck, let us know how it is @ 4 psi anyways...

 

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Posted: Wed Sep 28, 2005 2:58 am 
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Yeah 185 in an EB is still fun ( to start off with hehe )

So how does the boost climb related to rpm on SC motors? Say, at 3500rpm, what boost is it reaching? I'm only used to turbo's so dont know much about SC's... but wouldnt mind trying one in the future
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Posted: Wed Sep 28, 2005 3:06 am 
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CHEF wrote:
Yeah 185 in an EB is still fun ( to start off with hehe )

So how does the boost climb related to rpm on SC motors? Say, at 3500rpm, what boost is it reaching? I'm only used to turbo's so dont know much about SC's... but wouldnt mind trying one in the future


When I get my MAP sensor I will datalog how boost comes on but generally I find that at stall (around 2200-2500rpm) I will just start seeing boost (1-2psi), at 4000rpm I see about 5psi and it rises linearly till it peaks at around 6000-6500rpm
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