Ok, been running in the beast and noticed something rather odd on my way down to Leda the other day....

First, please note, if I put the accelerator to the floor this does NOT happen.

I was cruising down the motorway in 5th and having lots of fun putting my foot down when I noticed that if I 'feather' the accelerator (say I have it half down) I sometimes get a double chatter (it's almost like the engine is hesitating) when I'm expecting just 'moderate' acceleration. If I floor it it doesn't happen. Why is it happening when I'm accelerating?

Ideas?

Dave

 

Compressor surge. It's bad.

 

Not really sure what you mean by a double chatter, but sounds like you are just on that balance point between where the turbo is "just" stalling / surging.

 

Hmm, that's what I was dreading. However what I do not get is why it only does it when I'm feathering the throttle?! As I said it doesn't do it if I put it to the floor So what gives?

Dave

 

Its only when the compressor is being spun at a rate its trying to give out more airflow than the inlet will accept, with the throttle open its not an issue.

I doubt its a problem at all from a reliability point of view on a T34.

I may have misunderstood what you are saying, but the behaviour you are describing sounds very normal to me really.

 

it's doing it on part throttle because the VE of the engine is well down and it's making the turbo surge.

 

Has anyone else noticed that since Stu's article about turbos the use of the term VE had exponetially increased?

Or is it just me?

 

Your putting teh turbo into surge.. Look at your boost gauge and you will see the boost fluctuate at the same time.

 

this happens on two of my mates P1's..

they both have andy F TD05 20G turbos...

they think its a prob with the dump valves on the car but could it just be the turbo surging?

any way to confirm this?

 

dump valve and turbo surge sound different.

 

Indeed they do, but an overly sprung dump valve can cause the turbo to fall into surge before it releases...

 

Yes, fair point, likewise for if the flow rate of the DV is too low (hence on GT35R etc people tend to end up with two DV to stop the turbo surging)

 

on the P1's in question the whole car shakes really violently if you lift of ever so slightly

 

Compressor missmatch. Read my article in fast ford this month to learn what and why...

 

Hi Guys,

Thanks for the replies...just got in from Hospital so just had a chance to read them.

I am no engine expert (I try to understand) but I find it hard to believe that my T34 is producing more air than the head/inlet can consume?!

Anyway if it IS surge is it:

a) a problem?
b) possible to rectify?

I am using a T34 .63 and have no DV.

Thankyou please