924Board.org

[AppleBit]

Hi again Guys!

I found my problem- it's my warm-up regulator

I read this in the Tech Section some time ago:
(it's a little long)


One other improvement discussed by Probst in his book is the possibility of adding load-sensitive enrichment to the stock CIS system. The load sensitivity is such that, as manifold vacuum decreases, the mixture is enriched. The best and simplest way to do this is to replace the stock Control Pressure Regulator, or Warm-Up Regulator, with one that is vacuum-sensing. Bosch supplied these to various automakers, including Audi and Porsche, for higher-end cars. The basic function of this part is to enrich the mixture during warm-up; naturally it can also be made to do this as a function of a vacuum signal. However, the modification cannot be performed on a stock 924 unit, with any reasonable amount of work, so it is easier to swap in a load-sensing unit. For more details on the theory behind K-Jetronic, consult Probst's book.

The load-sensitive warm-up regulator should be found in the Audi 2V 5 cylinder motor. According to Dave Jalali, that should be the 86 & 87 Audi 5000TQ & 5000CS models and also the early 88-90 200TQ & 200CS models. In the event that there are two vacuum nipples on the new unit, the one in the base should be connected to a vacuum line from the intake manifold, as this is the one that will provide the load-sensitive enrichment.

This modification is especially useful on 931's and other turbo cars using K-Jetronic, as it will progress into boost-sensitive enrichment without any special modification, and without the installation of any electronics! It may be advisable to include a small valve in the vacuum/boost line between the intake and the regulator, to allow adjustment of the enrichment rate (just like pinching the line to the wastegate) to tune the response of the unit. If this is done, make sure to use a high-quality valve, such as a Clippard valve, to avoid failures.






My question is this: What regulator is it? I am going to buy one monday morning and I want to know how this will effect if I do not want the vacuum later for some reason? Does anyone know about this?

Thanks...

- Jon


_________________
Classic British Sports Car Restoration v6 + v8 Engine Conversion Swaps

Porsche 924 Wide Body LS1 Corvette 500 Horsepower Engine

[dpw928]

Jon,

In theory any CIS warm up (control pressure) regulator may be used if the inlet and outlet fittings are the same. On my two 928's (both 78's) the euro has the extra vacuum attachment and the US model doesn't. Whichever regulator you fit will need adjusted to match the 924's required control pressure. The adjustment is made by removing the circular cover and bumping the diaphram up or down. It can take a lot of trials and good CIS test gauges to get it correct. The WUR with the extra vacuum attachment are available from 928 International (www.928int.com). BTW I am not associated with 928 Int. except as a customer.

Dennis

[AppleBit]

Thanks Dennis for the answer,

I do have one quick question for you that you might know.

If there is no vacuum will the fuel pressure be lower thank what it should be on full throttle? I understand I have to take that circular cover and move it (and my dad is very familiar with german stuff- he worked on it for over 20 years)

Just wondering so I make sure I do this right...

Thanks!

- Jon


_________________
Classic British Sports Car Restoration v6 + v8 Engine Conversion Swaps

Porsche 924 Wide Body LS1 Corvette 500 Horsepower Engine

[dpw928]

Jon,

Low or no vacuum on the upper vacuum port will reduce control pressure which increases system pressure to the injectors.

Dennis