Excessive Turbo Lag

[Bleedski]

My 82 930 has excessive turbo lag. I was told it was the diverter valve, but was wondering if the fact that my smog pump is not functioning, since the drive belt is off, has anything to do with the lag. The diverter valve is plumbed to the smog pump on one side and goes under the engine to a pipe on the other side. Is it possible that since the smog pump is not turning that is a cause of the turbo lag?

[Tippy]

What RPM in 4th do you hit full boost?

[Norm K]

Is this a recent development or has it been this way all along?

Is noting that you still have a smog pump another way of saying your car is stock? If so, that'll go a long way toward explaining your lag.

[patina]

Maybe what you are experiencing is some kind of throttle issue? Remove the I/C and have a buddy step on the gas (car off obviously) and take a peek down the intake manifold and see if you are getting full throttle.

[Ronnie's.930]

Bleedski, the diverter valve you mention (going to smog pump/air injection pump) is not a valve that has anything to do with the turbocharger, rather, it directs air to the catalytic converter and so forth.

The turbocharger diverter valve is located in the stock, secondary intake manifold . . . if the seals are bad, it can leak air and the engine might idle and/or run rough due to an overly rich condition (air metering assembly thinks more air is needed than really is = rich), and you will hear a fairly loud, metallic "thunk" sound when you suddenly close the throttle (like throttle blipping at a stand still). I suppose the diverter valve piston could be stuck in its bore, but I'm not sure that would show as increased lag.

Below is a thread on the diverter valve that will help you ID it . .

Changing 930 dump-gaskets, pictures galore

[Ronnie's.930]

And as nkowi (better known as Normusmaximus) noted, if you have a stock turbocharger, then you will have "excessive lag".

[Norm K]

^^^^ That's "E"-Normusmaximus to you, Bucko!

[Ronnie's.930]

Originally Posted by nkowi

. . . "E"-Normusmaximus . . .

Norm, does the "E" refer to yer belly or yer buttocks?!?!?

[Noah930]

My car is stock, so I've got plenty of turbo lag (boost kicks in at around 3700 rpm), but the one time I felt I had excessive turbo lag was when the plastic throttle pedal became disconnected from the metal rod in back of it. The rod just got stuck in one of the waffles on the backside of the pedal. Must have happened when I was pulling the floor mats & carpet out for an autoX.

My smog pump isn't connected and that has no difference/effect on boost.

[Bleedski]

Thanks for the responses. Here are my answers. The car is full stock; I don't know what RPM in 4th it hits full boost; it's not a recent development; there is no throttle issue; my idle is very smooth at 950-1000 rpm after warm up. The idle is around 800 rpm cold, then to 950/1000 at warm up, all smooth. Thanks to Ronnie for the link. I've seen it before. I have a synapse diverter valve and wonder how that fits into the system. So what i have determined from these responses is that since I have a stock motor that turbo lag is standard operation fare. I probably don't have an issue, unless I want to start upgrading things.

[Norm K]

Originally Posted by Bleedski

Here are my answers. The car is full stock; I don't know what RPM in 4th it hits full boost; it's not a recent development; there is no throttle issue; my idle is very smooth at 950-1000 rpm after warm up.

The bold text above provides the simplest answer to your question. It's easy, albeit not all that inexpensive to address your lag. An upgrade of your exhaust system (headers and muffler) and turbo will go a long way toward lowering your car's boost threshold. Lots of opinions as to which products to use although budgets are often the deciding factor. One thing you can count on is lots of help from the tremendous aggregate knowledge base of this forum. Understand that you'll have to put up with a fair amount of junior high school-type banter that frequently appears from seemingly nowhere in threads that, up to that point, were on-topic and you'll get along just fine here.

[Ronnie's.930]

Originally Posted by nkowi

Understand that you'll have to put up with a fair amount of junior high school-type banter that frequently appears from seemingly nowhere in threads that, up to that point, were on-topic and you'll get along just fine here.

E-Normusmaximus is a real swinger . . . from vine to vine, that is!!! BUTT, at least he doesn't swing from nutsack to nutsack, like Paul!!!


Bleedski, I would be interested to hear about/see your Synapse diverter valve set-up, as that definitely does not fall into the "car is stock" category (takes some fairly significant "changing" to fit one of those - such as a longneck intercooler that eliminates the OEM, secondary intake manifold).

[quattrorunner]

He said full stock...then said the words synapses and diverter valve.
On another thread there may be problems with those parts but I don't want y confuse this issue.
I just want to point out that it wouldn't be bone stock with that part installed.

[Bleedski]

I purchased the diverter valve since a friend recommended it, but I have not installed since I could not figure out where to put it. So it is still stock.

[quattrorunner]

Gotcha

[Norm K]

Originally Posted by Ronnie's.930

E-Normusmaximus ...

Thank you.