Complete Kit Car – September 2019

Car Builder Solutions

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http://www.completekitcar.co.uk September 2019 93

Jason’s DeHavilland build is  nished...

which means he’s already hinting at the next project!

ONE FOR THE ROAD

T

his is my last Running Report for Complete Kit

Car, at least until my next build perhaps. As I

mentioned previously, the trip to Stoneleigh was

plagued with a mis ring engine, and I suspected

the fuel injectors. Ordering a new set didn’t cure the

problem, so I was completely stumped. I even did a compression

test to con rm no mechanical issues and it passed with excellent

compression on all cylinders.

After much head-scratching and further checks, I discovered the

throttle position sensor (TPS) was giving spurious readings. For

those not acquainted with fuel injection, the TPS usually gives a

low reading in the idle position and a high reading at full throttle.

Depending on the ECU used this could be shown in volts, for

example 0.52v at idle and 4.27v at full throttle, or in the case of my

Omex ECU shown as bits, for example 33bits at idle and 211bits

at full throttle.  e readings in between should increase steadily

and consistently, usually in a fairly linear fashion although there

can be a slight curve depending on make of TPS.

I monitored the signal on my laptop with the ECU powered

on but the engine not running, and it was quite revealing. It gave

a steady reading of 33bits in the idle position, but as I depressed

the accelerator that reading dropped to around 20bits suggesting

a negative throttle opening!  en as it opened more, the reading

jumped to 40-plus, then back to the 30s, then back up to the 50s,

before  nally giving steady readings near full throttle.

 is is the second TPS I’ve had from Jenvey because

Northampton Motosport discovered the  rst one gave poor

readings, although not quite as bad as this one. I therefore scoured

the internet for an alternative brand that would  t. With the new

TPS  tted, the readings are now rock solid at any throttle position,

even when the engine is running.

It was disappointing to  nd that the engine still wasn’t running

correctly, but I put that down to the new make of TPS giving

di erent readings to the old TPS, plus the fact the engine had been

tuned with a TPS that wasn’t reliable.

A dyno session at Mikeanics in Congleton, Cheshire, was

booked and the car driven carefully for the three-mile journey

to get there. However, Mike found that things still weren’t right

on the engine. Further investigation revealed one of the plugs

had coked up really badly, but a new set of plugs still didn’t cure

the poor running. Mike then checked the HT voltages from the

coil pack and discovered the coked up plug had shorted out and

damaged the coil driving cylinders two and  ve.

With a new coil pack sourced the same day, the tune was

completed successfully and, boy, what a di erence.  e engine runs

smoother than ever and we even saw a 2bhp increase in power.

Since the engine tune, I’ve also  tted an Idle Air Control Valve

to assist with cold starting and idling.  is was very easy to set up

on the Omex ECU and works a treat.

As with most kit cars, there’s always a little fettling to do once

you get a few miles on the clock, but I’m thoroughly enjoying it. So

much so, it’s already covered nearly 2000 miles.

Anyway, that’s it from me after nearly  ve years and 31 Running

Reports. I hope you all enjoyed reading them and, if you’re building

a DeHavilland DVT, you’re more than welcome to get in touch via

Complete Kit Car should you have any questions.

Faulty TPS needed to be replaced.

Better quality TPS now  tted.

Idle air control valve. IAC valve  tted and set-up.

JASON

BURRAGE

Project:

DeHavilland DVT GTS V6

Age: 44

Occupation:

Project manager

Project Start Date:

November 2014

Faulty TPS needed to be replaced.

092 Running Reports.indd 93 01/08/2019 12:50 pm