Jump to content

Megajolt V8 4.3 map


RogerD
 Share

Recommended Posts

Hi - I've seen a fair few example maps on here for 4,2 and 3.9 rovers but , according to the chap who sold me my car, I have a 4.3 (which from quick research tells me it must have been bored and stroked - it's not got TVR on it anywhere). I can't check the CC easily but I can tell you I have a dyno showing 250/250 bhp/torque at 5,8k, it develops power cleanly to 6.2k (or did, not 5.8k which is part of the reason I'm going EDIS/MJ) - if any of that info helps.

I'm looking for a 4.3 V8 map. I've seen 4.2 suggested maps so I assume trying one of those is the way to go?

Cheers

Link to comment
Share on other sites

6,200 rpm + rover v8? Must have different lifters (anti pump) rhoads?

I thought there was a stroker kit available from real steel a few years ago that was able to take a 3.5 up to about 4.3 using a reground chevy crankshaft new rods and pistons

Link to comment
Share on other sites

Numerous things about the engine build could affect what sort of spark map you might want, but starting with something known good & relatively "safe" and "conservative" from a similar V8 (or TBH almost any normal Rover V8 map) should do you fine, from there you're down to following the rules on how you tune the map to suit your engine. If it's a bit wacky / racy then you should really find out as much about it as possible and ideally speak to whoever built it, hopefully they'd be able to give you some guidance on things like max advance it can handle.

If it's a racy build you might need some (relatively) odd values in your spark table compared to "normal" engines to get the most out of it.

Link to comment
Share on other sites

I really don't know much about the engine history. I know is was built as a racer and then the builder changed his mind (it's a Westfield but there seems to be a lot of knowledge on here re. Megajolt).

I've had to have a larger crank pulley made as mine was too small so it under drove the water pump and alternator. The floor is all ally, the chassis is lightened. So a fair few racing hints. But I really don't know too much about the engine. I have some unverified history (a letter than came with the car from the original builder) which tells me:

Engine was overbored 20 thou, new pistons, bearings, ported cylinder heads, uprated cam shafts, Rhoades lifters, carb spacer and velocity stack.... but then he says he ripped it out and replaced it with a cross-bolted 4.2 - so I really have no idea! PLus, the history is for a car of a different reg!!

Still, I have a recent verified dyno print out from the previous owner who I do know and trust, and it shows 249.1Bhp peaks as 5400 but then carries on flat to a recorded 6100. Torque peaks at 265 Ftlb at 4450rpm then falls off as the power carries on.

When I got it it woudl cleanly push through over 6000 - I thought it was around 6200. Now it splutters at 5800.

Link to comment
Share on other sites

Hi Roger, I would have thought your engines spec (cam, head exhaust mods etc.) would have more bearing on your map than the small difference in capacity you are talking about. A 4.2 engine is actually 4275cc which is pretty near 4.3. I'm sure Nigel will tell you his maps are good to get an engine running and the fine tuning is to be carried out by you using the helpful tips provided on this forum.

Cheers

Steve - long time lurker, first post!

Link to comment
Share on other sites

Thanks for that. I know very little about RV8's to be honest.

I'm currently running on one of his safe maps. She drives ok but it clearly not totally ok. The engine kind of "pulses" between around 2k and 3.5k - I'm going to check my VR sensor bracket is tight and sturdy too.

I did notice that with a timing light she ticks over at 10 degrees advance as she should but she kind of flickers down 1 degree rythmically. Must be linked to the above.

Link to comment
Share on other sites

RV8's are very basic lumps.

Rule #1 of MS/MJ is that they cannot fix mechanical issues, so if there is some fault or problem (vacuum leak etc.) sort that out before changing settings. Recording data logs & looking at the graphs (log viewer) can show up issues quite nicely.

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

 Share

×
×
  • Create New...

Important Information

We use cookies to ensure you get the best experience. By using our website you agree to our Cookie Policy