Seems slower after service

[Fly Fifer]

I just had my 450 serviced and a misfiring at low revs problem sorted out.

Now the car, though still rapid, seems slower.

The garage told me that the air filter was totally gunged up.

Could it be that the air / fuel mixture is now less rich that the car isn't so fast?

Or, is it my imagination and that since the car is smoother now, it doesn't seem so fast?

Other's experiences with this would be appreciated.

[K4TRV]

Fly Fifer said:

[snippity] Could it be that the air / fuel mixture is now less rich that the car isn't so fast? Or, is it my imagination and that since the car is smoother now, it doesn't seem so fast? Other's experiences with this would be appreciated.[snip]

Your Fuel injection system is closed loop so the system keeps the Stoichimetric ratio at around 14.7, except during cold starting and other "limp home" modes.

With a blocked filter you'd be running a little more economically, because you may not have sufficient air for the max fuel (if filter was badly bocked, you could damage the Cat!) - it won't give you one without the other.

If you had a carbutettor fitted (or 2/3/4 of them), then I would expect the additional richness, but not additional performance you could "feel" - Stoichimetric 14.7 is "ideal" not for power or economy, but the optimum for both. Reduce the ratio and more power is produced, but again your filter would need to be able to provide sufficent air - you said it was chocked!! Increase the ratio and you'll be too lean and predetionation starts and temperature go sky high (melting plug electrodes).

If the garage didn't change your plugs, have a look at them - are they black/sooty or very white ?? The former is rich running, the latter too lean.

If filter has now been cleaned, I would respectfully suggest that you were/are just imagining that the car is slower - the induction system produces a unique noise and when an air filter is starting to reduce availabe air, the noise too changes. Again IMHO, would suggest it now makes the "correct" noises appropriate to rapid progesss.

Happy to be shot down, but it's my understanding of the Ottoman cycle.

Trev McM

[Fly Fifer]

Thanks for that Trev.

I'm guessing that it's in my head and that the car is just so much smoother.

Plugs were changed, as well as new shrouds and competition HT leads.

There is also that phenomenon that everyone is bound to experience when the speed begins stops being frightening.

Guess I'll just have to get a Tuscan

[trefor]

Check you have full travel on the throttle pedal - they may have adjusted it. Sounds daft, but quite common on these cars.

[Fly Fifer]

It's a good point Trefor. Did check with garage and they claim they didn't touch it.

Actually knew they didn't as I had the throttle cable replaced recently and it idles a bit fast since then and it still does.

BTW - checked out your web site - excellent.