Progressive V WOT loud pedal.

[B-Reight]

Any one noticed that their wedge performs better when feeding the throttle in instead of stamping on the throttle?

I've been doing some datalogging with my techedge 2J1 and have noticed that progressive throttle maintains a better AFR than WOT.

[_Absinthe_]

I have as a matter of fact. Although being a new wedge owner I thought it was just my imagination!

[ed_crouch]

Yet another reason to go Megasquirt!! 2J1 works well with MS2 aswell. I have one - great bit of kit.

[Wedg1e]

Yes. In fact I think every injected RV8 I've ever driven has been like that. Worst case is if you floor it from low revs: there's a gulp from the intake, then you have time to read your horoscope before the crank starts to spin up. To be fair, however much you lighten an RV8 it's never going to rev like a 4-pot twincam...

[honestjohntoo]

B-Reight said:

Any one noticed that their wedge performs better when feeding the throttle in instead of stamping on the throttle?

I've been doing some datalogging with my techedge 2J1 and have noticed that progressive throttle maintains a better AFR than WOT.

Depending upon the system, I'm thinking about it this way!

Stamping on the loud pedal creates an "enrichment double jeopardy" with both the "acceleration" and "full load" enrichment circuits being triggered at the same time by the throttle pot. Expressed another way - Too Rich, Too Soon! - Degrading efficiency during acceleration.

Feeding in the power as described triggers just the acceleration enrichment circuits initially and only when the throttle pot voltage reaches 75% of WOT (approx 3.3 volts) does full load enrichment occur.

When that eventually happens the enhanced enrichment is greedily gobbled up by the gasping engine now gagging for even more fuel. Discuss?

[gsx600]

I was talking to someone about my MS conversion the other day and they were suggesting to use the map sensor and tune by this, as more likely to get a smoother response when accelerating and a lower mpg if just cruising ! Might even get in the 20's

[adam quantrill]

With 300bph (and similar torques) on tap in a 1-tonne car I tend to feed the throttle in gently too.... in fact I do this in the 350i as well. It's a question of feeling for the wheelspin through your arse and compensating before things get too sideways...

Of course when it's on the straight and dry - FLOOR IT!

[honestjohntoo]

B-Reight said:

I've been doing some datalogging with my techedge 2J1 and have noticed that progressive throttle maintains a better AFR than WOT.

Typically, what were the logged progressive vs WOT AFR readings?

[B-Reight]

Well i wouldn't say too rich too soon. From yesterdays log stamping on the pedal from ~2000rpm would give me around 12.6, once the enrichments had done this would lean out between 13.5 and 14.5 as the revs rose- no good for power.

Feeding the pedal in i could maintain 12.5 to 13.2ish which is much better. Of course thats hard to do if your accelerating from low revs in a high gear as you can't feed in the accelerator to keep the enrichment going all the way to the redline.

This is however at 50psi rail pressure and modified spring tension, It's a best compromise. I'm pretty certain that whilst the 4CU system may be fine on a 3.5 landy but its pretty marginal on a 3.95 TVR. Anyway i've got my Jag AFM, just need to hunt round for some decent 153 or 157 injectors.

[honestjohntoo]

So, stamping is not "too rich - too soon" then? From the datalog it would seem that stamping on the pedal triggering full load enrichment, bypassed any subsequent acceleration enrichment leaving the engine running too lean. (Thinks! Of course it would, the throt pot becomes stationery at WOT after its initial thrust - doh!)

Perhaps a case of: stamping causes "not rich enough when needed"?

Edited by honestjohntoo on Thursday 8th April 21:15

[Wedg1e]

B-Reight said:

I'm pretty certain that whilst the 4CU system may be fine on a 3.5 landy but its pretty marginal on a 3.95 TVR. Anyway i've got my Jag AFM, just need to hunt round for some decent 153 or 157 injectors.

Like these?

http://cgi.ebay.co.uk/XJ-S-XJ40-Fuel-Injectors-Set...

Think I got my set of 8 for £60 but that was a few years ago, can't recall the Ebayer's name.

If anyone wants a set of standard 3.5L injectors (ie 105s) then you could do worse than buy a Jag V12 fuel rail, 'cos they use the same injectors as the RV8... but you get 50% more as spares

http://cgi.ebay.co.uk/Jaguar-V12-XJ12-S3-fuel-rail...

Edited by Wedg1e on Friday 9th April 02:31

[Transmitter Man]

Ian,

Excuse my ignorance but what are the advantages on using these Jag injectors?

Are they a strait swap?

I was told a couple of days ago that the stock TVR/RV8 injectors can only be checked for flow and spray pattern rather than stripped down like other injectors to replace jet, seal etc.

Is this so?

Phil
420 SEAC

[B-Reight]

Transmitter Man said:

Ian,

Excuse my ignorance but what are the advantages on using these Jag injectors?

Are they a strait swap?

I was told a couple of days ago that the stock TVR/RV8 injectors can only be checked for flow and spray pattern rather than stripped down like other injectors to replace jet, seal etc.

Is this so?

Phil
420 SEAC

Phil, with the stock 4CU mapping, which we can't change (unlike the hotwire system), the standard injectors don't really deliver enough fuel. They are only rated to 3bar and many a 4+ltr wedge needs 3.5+bar to get correct(ish) fuelling in my experience. I think ed crouch found the same as well. The Jag injectors have a higher flow rating so one doesn't need to use such a high rail pressure and can be used in conjunction with the larger bore AFM meter to reduce the restriction on getting mixture in.
They need modifiying to fit as they are designed for a different rail.

Edited by B-Reight on Friday 9th April 11:19

[gsx600]

Thought the jag injecotrs fitted to the standard rail on a flapper ? As pretty sure this is what I'm using

You would need to change the rail over if using the hot wire injectors - another job to do on my quest for more power ! (as already have the hotwire rail and injectors sitting in the shed)

[ed_crouch]

Yep, but Im in the midle of a megasquirt conversion, so I can just ask mine to open for a bit longer! Of course at high RPMs you get to the point where they would be open all the time, but that's not likely to be a problem until we get to 270ish horses on 190cc/min injectors.

Really Im doing it to make it drive better, get the throttle response a bit less fluffy and actually calibrate the hardware properly so I can get the most out of what I aleady have. When I want more grunt, I'll start playing with injectors and hardware upgrades, but that isnt really the game for me - I want a wedge that starts and drives really nicely, and has more consistent performance with maybe 3-5 more horses lassoed on the way. I shall try to retain the flap crackle and pop with some rich overrun bins (at the eventual expense of Lambda sensor life, but hey!). Meeeehhhhhhhhhhhhhhehehehehe.

Any more will be a total result.

Edited by ed_crouch on Friday 9th April 13:34

[Wedg1e]

gsx600 said:

Thought the jag injecotrs fitted to the standard rail on a flapper ? As pretty sure this is what I'm using

You would need to change the rail over if using the hot wire injectors - another job to do on my quest for more power ! (as already have the hotwire rail and injectors sitting in the shed)

Yes, no and maybe

There are some really high-flowing injectors used in certain conversions that were allegedly fitted to Jags, but from my research even the XJS V12 used the same injectors as the RV8 - and why not, after all the fuel requirement per cylinder is no more. So which Jag it is that is supposed to need massive amounts of fuel I never found out, and meanwhile standard Jag injectors DO fit the RV8 rail.

The revised XJ6 became the XJ40 which used a hotwire system and the injectors mentioned earlier, with the later fuel rail (using O-rings). They flow 214cc/ min where the standard RV8 3.5/3.9 injectors flow 180cc (or is it 190?). Also (as said above) they can do this at lower rail pressure. So instead of the usual bodge of winding up the rail pressure (as on the 390SE), for any given injector-open period more fuel is passed. I had to drop my fuel rail to 1.8Bar to get the car to run anywhere near properly; I can wind it up a bit and with a bootful of revs it's like being thrown off a cliff, the only time I ever felt like the 390 was REALLY fast.... the tradeoff being driveability elsewhere in the rev range.
All you need to do now is persuade enough air to climb in to match the available fuel, which is where the Jag AFM comes in because at WOT its bore cross-section is (supposedly) the limiting factor once you try to squeeze more power from the RV8.

To use the later injectors on the RV8 you simply saw off the plastic stub that carries the fuel rail O-ring. This exposes a steel core to which you can crimp the usual length of fuel hose and plumb to the old fuel rail stubs.
Arguably the later fuel rail has a larger bore and can shift more fuel, but for modest power gains I can confirm that the 214cc injectors do not run out of fuel on the standard rail

Look closely and you can make out the part number on the nearest injector...

Edited by Wedg1e on Friday 9th April 14:01

[Wedg1e]

Transmitter Man said:

I was told a couple of days ago that the stock TVR/RV8 injectors can only be checked for flow and spray pattern rather than stripped down like other injectors to replace jet, seal etc.

Is this so?

Phil
420 SEAC

I think you can change the plastic nose cover and the inlet filter but not sure beyond that.

[B@man]

Looks like Next weekend I will mainly be playing with my Innovate wideband.

I now have aux inputs connected to the TPS, AFM and the new ignition system has provided a RPM input that works (hopefully) with the LM-2.

I must admit I don't remember the AFR being "better" when feeding in the throttle last time I had the wideband in use. Due to the AFR being 18:1 @ WOT we concentrated on fixing that and just did a quick check for over fuelling everywhere else. I'm also running at 50 psi rail pressure.

Now the RPM input is working I can log some data for progressive and "bootfull" runs and see what is going on, I may even be able to get the Map data from the MegaJolt as that will also data log.

Too many toys....

Damn my MJ comm's lead is in the stuck closed glovebox....

Edited by B@man on Saturday 10th April 09:32