Engine Blips

[Guest Daz]

All,

 

I have a little snag that is annoying me; mainly because it has me stumped. The car starts no problem, first time every time. The car idles fine. However, after the auto choke comes out is when the problem raises its little head. The car still idles fine, and it runs as sweet as a nut at anything over 1500rpm. The problem is when you pull away, or drive slowly in heavy traffic, the engine revs die off before picking back up and launching me away. The revs also die off if I blip the throttle while the car is warm and idling.

 

It has only started doing this since I fitted a Kent FR30 cam, dizzy and DGAS 38 carb, then had the lot tuned by a mobile tuner. The only thing I am already aware of that could be an influence is that the 'new' dizzy turned out to be for a 1.6 Pinto and not a 2.0. And I also fitted a brand new in-line fuel filter that came with the carb.

 

If I pull away at around 3000 revs I have no problems (apart from attracting questionable glances!), so the problem is only at low revs. I am looking for pointers and any you may have would be appreciated.

 

Daz

[Guest daveg]

Daz

 

If the problem started when you fitted all those items...then one of them is causing the problem. You could try back-tracking, remove each item and fit original until problem solved, then you know the offending item.

 

My guess would be the carb, when you blip the throttle you use the next jet after the idle jet, you are getting a weak mixture at this point (my guess)

 

Also check for air leaks.

 

Dave

[Guest Robin Allison]

Daz

The only way to tune the new set-up you have is to have a session on a rolling road. The mobile tuner can only set-up the timing and mixture at idle/ fast idle, to check the carb is set-up for you'r engine it has to be under load this can only be done on a rolling road.

Its usualy money well spent, and quite an experence to be stood next to your car with the engine thrashing about 7000 RPM (It realy makes you nervous). From the set-up you have expect about 100 to 105 BHP at the wheels.

 

Rob...

[Guest bloke]

i'm interested to know how much torque and hense acceleration times of this set up compared to standard lump???

not picking my kit up for a month so probably wont be getting an answer in practice for ages!!!!!!!!!!

know this message is off track from th original but hope you dont mind

[Guest Daz]

Thanks for the responses so far.

 

Bloke, I do not know exact figures for torque but as the FR30 is a high torque sports cam it has made a hell of a difference. Acceleration figures have improved dramatically - it now propels me from 0-60, with my 15-yr old son on board to check the time, in just under 6.5 secs. Nice.

 

Daz

[Guest bloke]

daz

 

v nice!!!

what was time bfore cam mod?

bloke

[Guest Daz]

I checked it without assistance from my son the first time, and clocked around 8.5 - 9 secs. Only an estimate though, using a second hand on a proper watch. That was with the 2.0 in standard tune with a DFTH 30/34 electronic carb that is controlled by the ECU. Hence the need to tinker.

 

Daz

[Guest John Walton]

Hi Daz

I have much the same problem and much the same set-up as you.

It sounds like the DGAS.

I'm experimenting with a bigger pump jet.

[Guest Simon cooper]

Hi Guys,

The prob is on the enrichment circuit in the carb. check the enrichment diaphragm and that the jet is not blocked. 100% guaranteed.

The rolling road is not vital and can achieve very little with a DGAS . checking what other guys have for jets is as close as you need. If you are on standard disi, the tuner is even more restricted by the engines base timing which on pinto's is 10-12 degrees. Save your money and by a vernier pulley instead, it will give you more power when set right. Rollers are more for 40's and 45's. There is a lot of psychology involved (not intentional).

Simon

[Guest Daz]

OK all,

 

I think I found the problem. I noticed that when I first fitted the carb I never had a problem with the engine dying. I started to think about what had been doen to the car since then, when suddenly it came to me in a flash of inspiration.

 

When the carb came I fitted it as a straight swap for the one that was on there. The fuel came from the pump and into the vapour separator. From there was the fuel return line to the tank and a feed to the carb. On the carb there was the inlet port for the fuel (no problem there) and an outlet port to connect to the return line. Since the return line was already plumbed in I just blocked the outlet port. The carb worked a treat.

 

However, (pause for effect), I though it was inelegant and as I had the mobile tuner coming I decided to replumb the fuel system so it didn't look so gash. Out went the vapour separator. The fuel return was attached straight onto the outlet of the carb. The fuel line was plumbed from the fuel pump, into an in-line fuel filter then into the carb. Nice and simple. The tuner came and did his stuff and it wasn't until after quite a few miles that I noticed the little problem.

 

Tonight I went back and looked at the fuel system. I took the fuel filter out so that the fuel line goes straight from the fuel pump into the carb, then out to the retrun line and back to the tank. Even simpler! Now it works a treat - no engine blips or fall off of engine revs during acceleration. I have a theory that the filter was preventing the full fuel pressure from being transferred into the fuel chamber. I also noticed that the filter always seemed to have an air bubble in it, but that may be irrelevant.

 

Now I need to think about locating the filter elsewhere in the fuel line.

 

Daz

[Bob Tucker]

Hi John,

to add a few things to our previous emails re DGAS setups....

I have a single fuel pipe (no return)

and use a Filter King combined filter & pressure regulator.

Bob.