The V8 Owners Forum -

Posted: **Wed Oct 14, 2009 4:28 pm**

I'm the owner of a Rover SD1 Vitesse Twin Throttle Plenum (with flapper Efi) with an engine rebuilt by JE Engineering (work carried out while under ownership of previous owner). Its the driving characteristics of the car that I cant get my head around. Being a novice in V8's, when I purchased the car it didn't enter my head that the cars driving characteristics may differ from a standard V8 Efi with standard cam. I've been skim reading some posts and one stood out in particular from Ian Anderson about his JE102 cam in his GT40 replica and, I quote,

"Try to get it to go along in 3rd at 30mph 1700 rpm and it will not cruise in a line of traffic and bucks like a bronco on kangaroo petrol."

this is what happens to me, but the difference is that my engine is supposed to have a JE101 cam and from what I've read, the JE101 is a mild fast road cam.

Here's the spec (what previous owner remembers) :-

engine acid dipped and totally rebuilt by JE Engineering
heads fully balanced & ported
double-valve springs
triple-valve seats
JE101 cam
adjustable Vernier timing chain set
centre pull plenum butterflies
adjustable fuel pressure
high pressure oil pump with sperm-type relief valve
JE Engineering stainless steel exhaust system, incl tubular manifolds.
KONI adjustable shocks
JE uprated lowered springs
Mark Adams E-Drive ECU for FLAPPER-type EFi

When I'm out in it around town or residential areas (30 limit), very rarely do I get into 3rd and be able to stay in 3rd at 30mph (car starts to buck) and so I drop it to 2nd until I leave the 30 area and then perhaps get it into 3rd doing 40mph or more. The car just wants to go fast and I always seem to find myself stuck behind slower traffic always holding the car back.

The Mark Adams E-drive ECU is something I added as the ECU needed remanufacturing as it had a bad intermittant fuelling fault.

Are these the driving characteristics you would expect from an engine with the above spec?

Is the above spec what someone would have done if they had a heavy right foot?

Sorry to go on

Posted: **Thu Oct 15, 2009 8:59 am**

Do you know what the duration of the camshaft is?

It does indeed sound as if it has not been built as a general road going car.

Ron.

Posted: **Thu Oct 15, 2009 9:39 am**

Hi
The bucking feature is generally lean mixture going even leaner as you transition the throttle, even my vogue RR on a 3.9 standard engine could be induced to do it, it is because the light throttle fueling is very lean on all rover v8 ecu's. A mark adams ecu is just a modified standard ecu, the basic map is the same with some scaling modifiers and "adjustments" hence it has the basic charictoristic of the standard engine. You have then modified the engine and taken it further from standard so the fueling is even further out, hence the situation you (and Ian) have.
Your choices are, fit a mapable aftermarket ecu (with wide band lambda sensors and solve the problem, take it to Mark adams and spend alot of money on a rolling road trying to solve it before getting pi$$ed off with EFI generally and bin it for a Holley spending yet more money setting it up and still have dubious part throttle responce, bin the whole lot now and fit a Holley saving all the money on the Mark adams sort out.
Personally I would replace the ecu and see how well a properly set up mapable ECU can transform your engine, overall the second cheepest option (by about £200) on initial outlay and as you can tune it by driving it on the road it will save a fortune in rolling road time.
Mike

Posted: **Thu Oct 15, 2009 2:13 pm**

There is an issue that may be relevant - and that's airflow through the AFM.

It may be that with the exact valve timing and port tuning you have, the air-flow at certain throttle / engine speed combos is very 'lumpy', maybe even resonating, in the inlet tract.

If this is the case, then the AFM will be reading rubbish, and play hell with the mixture.......

It must be a problem:

otherwise you wouldn't get that sort of tomfoolery show above going on.

Quite how you test for it though is beyond me.

Just my 2pm worth anyway.

Chris.

Posted: **Thu Oct 15, 2009 2:48 pm**

In addition to the correct onservations above, I would add the the problem is caused by the wider overlap of the cam which causes exhaust gas pulse reversion back through the airflow meter causing it to misread fuelling requirements by reading the gas flow as almost double.

I also have a pet theory that this also effects the vacuum in the manifold which on a light throttle could cause the vacuum timing advance to fluctuate quite extremely further agravating the problem.

I have just recommended to someone else with the same problem as yourself to try disconnecting the vacuum pipe from the distributor, plugging it so the mixture isn't weakened, and then see if it makes any improvement, he hasn't reported back yet so perhaps you would like to give it a try and let us know how you get on.

Kevin.

Posted: **Thu Oct 15, 2009 3:42 pm**

CastleMGBV8 wrote:
I have just recommended to someone else with the same problem as yourself to try disconnecting the vacuum pipe from the distributor, plugging it so the mixture isn't weakened, and then see if it makes any improvement, he hasn't reported back yet so perhaps you would like to give it a try and let us know how you get on.

Kevin.

I'm probably going to be viewed as a bit of a nut for saying this, but my distributor doesn't have a vacuum pipe

???

The funny looking 'flying saucer' thingy attached to the side of the distributor that I've seen on other cars and on RPi's website photos doesn't exist on my distributor, which is something that has always puzzled me. It was like that when I got the car, the previous owner had all the engine work carried out in the 90's. Why would they take it off?

Posted: **Thu Oct 15, 2009 3:44 pm**

kiwicar wrote:Hi

Personally I would replace the ecu and see how well a properly set up mapable ECU can transform your engine, overall the second cheepest option (by about £200) on initial outlay and as you can tune it by driving it on the road it will save a fortune in rolling road time.
Mike

Are we talking 'Hotwire' sort of thing?

Posted: **Thu Oct 15, 2009 3:48 pm**

RoverP6B wrote:Do you know what the duration of the camshaft is?

It does indeed sound as if it has not been built as a general road going car.

Ron.

Am a little thick when it comes to the technical aspects of camshafts, still learning. In a book, it lists the values of the JE101 as Timing 20/65/25/20, Period 265/225 degree, Valve Lift 430", would one of those be the duration?

Posted: **Thu Oct 15, 2009 3:50 pm**

ChrisJC wrote:
Just my 2pm worth anyway.

Chris.

Going by the picture, I see what you mean.

Posted: **Thu Oct 15, 2009 4:20 pm**

Why does some one not make a replacement ECU for the Hotwire syatem that you can unplug the Lucas (Prince of Darkness one) and plug in another one? Sue some want a manifold pressure instead of airflow meter and most need a lambda / o2 sensor

But to change to megasquirt I'd need to change the Ecu (£250), fit a toothed wheel (£60 plus sensor £60)(no space), change wiring, change sensors (£ 60 - £100), add 2 o2 jobbies (£300) etc After all the Lucas one may not have been perfect but it did pretty well - surely not that major job to make it with better chips and allow some adjustment. (With all these costs it's probably cheaper to buy quad downdrafts and have them tuned professionally.

Ian

Posted: **Thu Oct 15, 2009 4:26 pm**

The "hotwire" bit is the air flow meter, the ECU is the electronic box that Mark adam's chip (s) plug into, I am recommending the replacment of the electronics box with either a Megasquirt, Extra efi, emerald, Vems, ECU (and at the same time you can bin the air flow meter.
The timng of your cam is mild so overlap is not really likley to be an issue, the duration is the 265/225 bit, 265 degrees between .003" of lift (ie just off the seat) the 225 is the .05 lift duration in crank degrees.
the 20/65/ 25/20 are the timing events , the inlet valve opens (just lifts off the seat) at 20before top dead centre, closes 65 degrees ATDC exhaust opens 25 degrees before bottom dead centre and closes 20 degrees after top dead center, that gives 40 degrees total overlap, but as flow effectivly starts at .05 lift and this timing is 40 degrees less than seat timing then you have a 0 overlap cam as far as flow is concerned.
Best regards
Mike

Posted: **Thu Oct 15, 2009 4:47 pm**

Oh bugger!

Just realised I'm totally screwed

! Should have put this at the beginning of the post. I see that Jon Anderson is on Hotwire Efi, and that any recommended ECU changes would be for a Hotwire system. Problem is I'm living in the dark ages with the original FLAPPER type Efi system.

Posted: **Fri Oct 16, 2009 6:38 am**

Too much ignition advance can cause the symtoms described, try backing the timing off a couple of degrees and going for a drive.
Assuming the EFI unit does not control the sparks ?

Mark

Posted: **Fri Oct 16, 2009 8:59 am**

Ian Anderson wrote:Why does some one not make a replacement ECU for the Hotwire syatem that you can unplug the Lucas (Prince of Darkness one) and plug in another one? Sue some want a manifold pressure instead of airflow meter and most need a lambda / o2 sensor

But to change to megasquirt I'd need to change the Ecu (£250), fit a toothed wheel (£60 plus sensor £60)(no space), change wiring, change sensors (£ 60 - £100), add 2 o2 jobbies (£300) etc After all the Lucas one may not have been perfect but it did pretty well - surely not that major job to make it with better chips and allow some adjustment. (With all these costs it's probably cheaper to buy quad downdrafts and have them tuned professionally.

Ian

Hmmm, most alternate ecus can run with the dizzy, your existing wiring & lambda sensors, don't confuse replacement and the subsequent upgrades that folks choose to install. You just have to lock the dizzy advance, and the ecu controls all the advance to the coil, bit of care is needed positioning the dizzy but thats no more than usual really.

Installing an ecu with the dizzy has a lot of merits, which also affect the budget significantly. I do wonder why it is not done more often, even if just as a stepping stone in the grand scheme;)

Posted: **Sat Oct 17, 2009 12:01 am**

JEV8SD1TP wrote:
CastleMGBV8 wrote: I'm probably going to be viewed as a bit of a nut for saying this, but my distributor doesn't have a vacuum pipe ???

The funny looking 'flying saucer' thingy attached to the side of the distributor that I've seen on other cars and on RPi's website photos doesn't exist on my distributor, which is something that has always puzzled me. It was like that when I got the car, the previous owner had all the engine work carried out in the 90's. Why would they take it off?
That probably means you have a race distributer. great for WOT and racing, but rubish for fuel economy etc

The V8 Owners Forum -

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