Supercharger Oddity!

[TheDon]

Well i got my TTE upgraded spring assembly and fitted it quickly and left the house. now what i had forgotten to do was remove the old coil spring.

Power was quite noticbly up on the standard spring alone, and there was less "lag" like feel when changing gear. The main difference was that there was a very quiet "dump valve" style let off. but again power was up.

During that drive i stoped to remove the old spring from the system, instantly the whoosh noise was back between changing gears but also a definately different power curve!

i also checked to make sure the valve was still opening and it definatly was, no problems at all.

now was this just a strange thing or was this a bad thing? im not even sure what the bypass is for fully, but i miss that extra grunt it seemed to have

[SteveAudioX]

So what was better, your original weak spring or the upgrade?

[aido]

Chris, I had both on originally mate when mine was fitted, but found a post on here somewhere that said that basically having both is not recommended since it puts extra load on the throttle assembly or something - can't remember where I read that but it was somewhere on here!

And don't worry about the dump valve noise - not sure if you've heard a car with the sc induction kit when she's going full pelt but it's about 100 times louder than the bypass noise you're currently hearing - sounds great when you get used to it - you eventually learn to time it so you change gear at 6k rpm just as you pass a group of people - their heads about snap off :P

[TheDon]

it was better with both of the springs on, but on their own i notice no difference.

Is it that it puts too much strain on that metal arm on the throttle?

would be interesting to find a slightly uprated spring to have a play with!

Oh i definately love that whoosh noise, lots of children and old ladies scared by it !!!

[aido]

You'll be scaring the **** out of people when the induction is on mate, lots of fun :)

[Rob]

The spring is there to return the flap valve assembly of the bypass to the open position to allow air to recirculate in the system when it is not in the "boost condition - ie with the valve closed or when the throttle is at the full range of travel.

In theory there should be no difference in total engine power if u have 1 or 2 springs on the bypass assembly when you want "boost" as the purpose of the spring/s is only to return the valve to the open position.

If 2 springs are fitted then the valve will have more force to open, so i would say that this is why u are hearing a different pitch/note when changing gear with 2 springs, as the valve will be opening very,very,very slightly quicker resulting in less of a pressure drop within the system and thus causing the percieved "power increase".

Obviously the position of the valve is relative to the throttle position eg throttle to the floor = valve fully closed, vise-versa and at increments between the ranges of travel (providing the valve cable adjuster has been set properly)

It is important to understand how the supercharger works ( I will defer from using the name compressor as it is not one in the true sense, the TTE "compressor" is an eaton roots blower which provides "boost" by providing excess air within the system and as such a pressure is built up within the system, not within the casings of the supercharger itself - in effect the supercharger is just an air pump) so when the bypass valve opens eg when changing gear it will alllow the valve to open and recirculate some of the pressurised air, thus causing a pressure drop in the system, and this will take a small amount of time to build back up once the valve has closed ( when the throttle is depressed again)

The issue about the extra force on the throttle bypass assembly is from information I recieved from Gerald Bonengel, Principle Engineer for Engine Development at TTE. I sent him an email regarding the correct positioning/adjustment of the bypass valve assembly - his reply was to say that it is not only a "boost" build up matter, if the bypass was incorrectly adjusted then it can place extra load on the clutch assy of the electronic throttle and then this would cause it to disconnect resulting in engine power loss.

I hope that this answers some of your questions, if u have any more please post them here or send me an email, and ill try to answer them.

cheers rob.

[TheDon]

cheers for that, makes a lot more sense now! altho my brain has overloaded a little. must have a power nap!

[marcus]

must have a power nap!

PMSL

[aido]

Did you get this sorted in the end Chris?

[Bazza]

just noticed on the TTE website

on compressors for the IS200

no spring !!

or not where i can see it ??

[aido]

Looks like there is something different hanging out of the back left hand side exit - is that the bypass pipe?

There was talk about other bypass methods ages ago, maybe they tested it out on this model?

[Rob]

Barry, it is a vacuum bypass that is fitted in that picture, the benefits are that it will get rid of the horrible linkage system and thus remove the possible problems with the loading on the throttle servo.

last week i ordered a vacuum bypass and am awaiting delivery so watch this space................................

also noticed the price is in DM, so that picture is old, but the airbox is of the new style and that there are nuts instead of inserts on the airbox screws, also the rad cap appears to have a plastic cover, an d of course the painted bypass tube.

i can roughly translate it but ill wait till the GF is back to get it done properly!

[Bazza]

Barry, it is a vacuum bypass that is fitted in that picture, the benefits are that it will get rid of the horrible linkage system and thus remove the possible problems with the loading on the throttle servo.

last week i ordered a vacuum bypass and am awaiting delivery so watch this space................................

also noticed the price is in DM, so that picture is old, but the airbox is of the new style and that there are nuts instead of inserts on the airbox screws, also the rad cap appears to have a plastic cover, an d of course the painted bypass tube.

i can roughly translate it but ill wait till the GF is back to get it done properly!

rob,

can you keep in touch with this as i would be interested in one

[Rob]

i will do mate, ill let u know when i have revcieved it( it is out of stock at the mo) and then will do a bit of testing to see how it performs etc and of course i will let people know the results.

[TonyGoose]

I think you'll find that picture is pretty old.

It's the same one as in the brochure for the compressor kit.

Seem to remember asking about it before - and...

vacuum bypass was used initially but replaced with cable.

The airbox is the old type too - fibreglass...

Some pipes were revised too... diameter etc.

Incidentally, saw vacuum bypass like that on an RX.

[Rob]

looked like the new airbox - just because of the finish, but might be the picture.