15 replies to this topic

[Jux]

Heya :)

 

I fitted a SC 7Port head to my Engine. Im using the +60 pistons, have a CR of 11.25, a SW23 cam, 125ccm injectors and Jenvry throttle bodies.

I got the base file from SC and it works suprisingly well. The engine starts up fine, runs a bit rich for maybe 1min and then runs really fine.

 

AFR rather lean on cruise and rich on power. Maybe a bit too rich even, especially at low rpm, but that are details i have to sort out at the RR.

 

The problem i have now is that i dont get the idle down. I have closed the throttle bodies as far as possible, checked for leaks and still the engine idles at 1700rpm. I get it down to 1100 by the idle control to 1050-1100rpm. The idle control retards the ignition to 0 to + 2 degree. 

 

The engine still idles very smooth and fine - picks up throttle nice. BUT it gets hot in idle.

When driving it does not get hot, even if i spank it up a mountain. It seems the harder you drive i the cooler it gets. But at idle at the traffic light i can watch the temperature rising, starting a sweat how long it will take.

 

Is it possible that the massivly retarded ignition causes this in idle?

Anyone has simular experiences? I read that 7ports trend to idle high because they get too much air - is there a solution for that problem?

 

Best regards

[sonscar]

Retarded ignition will cause overheating very quickly.ITBs pass lots of air even when almost fully closed so idle can be problematical.Do you have an idle air valve?Just some random thoughts,Steve..

[IronmanG]

Where are you based
Mine idles about 900

Edited by IronmanG, 21 July 2022 - 05:41 PM.

[Jux]

I dont have a Idle air valve. Only the air valves for syncronisation, but they are all closed and the Throttlebodies are syncronised perfectly.

I am the MED Extreme front radiator (its a 1275GT). Although its half covered it cools very well when driving and i have a electric fan with a thermo switch at 85°C. 

 

 

 

I am from Austria 

[mini13]

is this the billet head and throttles or the cast head with the jenvey dcoe style throttles?

[Midas Mk1]

SW23 race cam - surely that won't idle low. 

[sonikk4]

is this the billet head and throttles or the cast head with the jenvey dcoe style throttles?

 

His first post says Jenvey Throttle bodies. Were the ITB's an option on the billet head as i have their own Billet throttle bodies on a Billet head. (still not fully built yet!!!) 

[sonscar]

If you close the butterflies completely does it stop?Steve..

[Jux]

Its the cast alloy head from SC with 40mm Jenvey Throttle Bodies.

 

The butterflies are closed as far as possible - it does not stop. I checked for leaks several times too but couldnt find any. Also if it would leak it wouldnt run so well on idle.

[sonscar]

But it is not running well at idle,the air is coming from somewhere.Fuel, air,spark,compression engine runs.More air,thus more fuel so runs faster,,,,you get the idea.Start again from the beginning and assume nothing.Steve..

[Jux]

Well it does idle very stable and smoothly. Both on 15deg advance at 1700rpm and 1-2deg at 1050 rpm.

Also in both situations the throttle bodies are syncroniced. I also checked for leaks with break cleaner around the throttle bodies and got no response.

 

AFR is stable at 14.7 - 15 at idle

[mini13]

I would be looking to get a flow meter on there to check they havent got screwed up, also check the plugs are all the same colour.

 

the Jenveys have idle bypads screws which you shouldnt need to adjust.... but maybe they've been screwed with, or maybe they set them different for differnt size motors.

[PoolGuy]

 

The butterflies are closed as far as possible 

 

 

But it is not running well at idle,the air is coming from somewhere.

Steve is right, air has to be coming from somewhere. Don't be confused by the stable idle, the ECU is doing that, switch off the idle control for now. Also, is the 14.7 air being controlled by the ecu in closed loop at idle too? 

[mini13]

I should add, that even if the AFR is right ( because the ECU is correcting it) you could have 3 rich cylinders and one that is lean causing the excess heat and rpm ( hence my comment about checking plug colour)

[Jux]

I did check the bypass screws and they are all closed.

 

@mini13 what do you mean with a flow meter. I have a synchrometer like this:

https://www.speciali...plications.html

It reads the same on all 4 cylinders.

 

Only thing i didnt check yet are the plug colours - guess i do that next. Its a bit of work on the 7port ;)

 

Is it possible that the Air going by the butterfly when its closed (its never 100% air tight) is enough to cause the high idle?