Low Boost

[KVJ 786]

Hi Guys

Been a while since I needed to obtain info on a problem I may have developed.

Well I noticed ny S4S recently felt like it was lacking pull on normal driving. So Last night I took her out on a long drive to give it full throtle where possible.

What I noticed was on full throtle I only seem to get 50-55% boost on my gauge and that is not right as before the gauge would read max.

I am running everything stock with electrc pump for charge cooler. The cooler seems normal after a run when I touch the top which feels cool. Oh I am also running with chip number 5 but that has been in the ecu for a long time now.

So today I jacked the back up and looked underneath for anything out of place. The only thing I found was the exhaust bolts 3 of them between cat and muffler were loose but in place. EBPV has been removed previously and fitted with a spacer ring in between.

My question is could this cause the boost to cut down if there was a exhaust leak in that area? or is something more to my problem. BTW the turbo actuator looks very rusty as my guess probably original since 1995

Any suggestions to what else I should check or do would be greatly appreciated as always.

Cheers

Ameer

[tjs98jetta]

Cold be a lot of things, including wastegate actuator. That's easy to check, there is a procedure on LEW:

http://www.lotusespritworld.com/EGuides/ETechnical/Wastegate.html

I had a leak in the square gasket between the exhaust manifold and the turbo input, that also possibly limited my boost. Look for sooting around that area. Otherwise, could be a number of other things. You'd need to look at the engine parameters while running using Freescan or Espritmon. Wouldn't be surprised if it's the wastegate actuator though, I had to replace mine some time ago. A leak further down the exhaust system doesn't seem a likely cause, although will likely give you some popping as you lift off the gas.

[jonwat]

A blown "check engine" light bulb will restrict boost, does the CEL come on when you turn the ignition on?

If it does but goes out once the engine has started it's still worth running Freescan to check everything is ok.

http://www.lotusespr...e/freescan.html

[KVJ 786]

Hi Guys

Today I got 3 new bolts and nuts with washers and tightened up the cat and exhaust. Started my car up and noticed some rattling noise inside the cat area. This is starting to tell me naybe the cat is breahing up inside.

Ran it for a while and the rattling stopped, switched off and started again still no more rattle. Havent taken her out for a drive yet as I think I will run freescan first.

Will report back what I find.

Thanks for your input.

Ameer

[dodge1979]

Is your engine temp getting up to normal as it should?

[KVJ 786]

Hi Again

Took her out today and floored it for a short burst and got 75% boost. Temp is up to spec. I will run freescan later but dont really know what I would looking for from the results unless I get an error code.

Will report back later

Cheers

Ameer

[jonwat]

So, does your check engine light come on when you turn on the ignition, if it doesn't the bulb has blown

[fflyingdog]

Get the error code(if it throws up any) it may or may not be usefull, but its a step in the right direction.a leak further down as you have wont make a jot of difference to you developing boost as its after the turbo has finished with the gases its just getting rid of the gas/noise and some scaveging effect,but effectivcely the faster you get rid of the exhaust gas the better,there is a theory but i forget what it is exactly ,but basically its the high pressure gas(exhaust manifold side) spins the turbine then through the turbo to the low pressure side and exiting as low pressure gas,thankyou Mr Bernoulli

.As John said check your CEL comes on when you turn the ignition on,i have been looking at the wiring diagram and you could be chasing your tale without a good Freescan printout,you could have a bad TPS or Mat sensor a loose vac hose ............see where this going ??

Best of luck...its only a machine man put it together man can fix it.

[KVJ 786]

Hi John

Yes the check engine does come on.

Been busy recently so will chek freescan over the weekend and report back.

Cheers

Ameer

[Rich H]

Rattle by the top of the cat is what I had.

It was the wastegate flapper valve not seating properly as the WG actuator wasn't tight enough.

I made the actuator rod another half turn shorter and the rattle stopped.

It would be like having the WG open all the time.

[KVJ 786]

Hi Rich

That is something I would consider replacing as it looks rusty and coroded. This item is vital to the control of the turbo.

Thanks for your input.

Will look at that over fhe weekend.

Cheers

Ameer

[Rich H]

The flapper valve is loosely located on the lever so will rattle if it's not held down tightly.

[KVJ 786]

Hi Guys

Update to my boost problem.

As I have been away for a few weeks in UK and just returned back to Florida I did not check my car until now.

Today I took her out on the highway and gave it some welly and the boost was back to full BUT now it does something different,

AS I floor my car takes off as it should then I feel engine miss fire and the boost gauge goes to ZERO then returns to normal when I ease foot off the throttle. If I throttle slowly the boost builds up evenly but if I floor it it cuts out.

Any ideas to what I have going on, my guess could it be the wastegate actuator or is it more serious.

Any comment greatly appreciated to point me in the right direction.

Cheers

Ameer

[Bibs]

Check your MAP pipe Ameer...

[fflyingdog]

Have you a dump valve fitted ? Check its not leaking back through.