lacking in bhp a bit...

[thenick]

Right, next hurdle in the Emerald project...

I got it running ok and drove it down to Emerald at the weekend for Dave to have a look at as I ran out of holiday to finish it. I got a call a while ago and Dave reported that it is now running ok and torque/bhp are up from 180/125 to a slightly more respectable 295/238. I haven't seen the car obviously but Dave said that it doesn't seem to want to rev very much and peak power comes in at late 4's and seems to tail off during the 5's. He ran a pressure sensor in the intake to check th airflow and found there to be almost no vaccum at all in the inlet thanks to the big bore stuff so there's no lack of air and nothing else that appears immediatly apparent.

Now before I ring a specialist tomorrow morning to see if something else is likely to need attention, I just thought i'd ask around on here as there are several knowledgable people around. Does anyone have an idea what could be causing this lack of top end? All I can think of is that there may be some sort of cam issue perhaps...


The engine spec is as follows:

1997 450 serp
all the ACT induction stuff and cf trumpets etc
72mm throttle
MC1 cam installed by Dave Batty around March/April last year
ACT decat manifolds and exhaust
Emerald ECU (obviously) running wasted spark on coilpacks

Any clues??

Edited by thenick on Tuesday 29th January 18:56

[v8 racing]

To be honest those power figures seem bang on the money for me, dont forget a 450 is a mildly breathed on stock range rover engine that from the factory made just over 200 bhp, if you have standard heads on it then that will be the restriction.

[thenick]

Really? I thought the hp was meant to be a little closer to the torque figures than that? Dave seemed to think that something wasn't right anyway as the power was tailing off a little early. Or is it supposed to be like that...?

[v8 racing]

seriously there is not a chance would a 450 make near on 300 bhp in road going trim, the most you can expect from a genuine rolling road is around 285 and thats with more of a cam than an mc1 and big valve heads, ported inlet manifold trumpetbase and the emerald etc..

[Meatball]

Apart from the emerald stuff im running similar mods to yourself the only big difference i would say is the heads as mine wore big valve as standard and the ports were worked out to stage 3/4 by Jamie at CRE. Did you change your inlet manifold to match the larger trumpet base to the heads? As a comparison im making 298 @ 6000

[thenick]

I wasn't expecting 300 horses for sure, but from what Dave was saying, it seemed to be running out of puff a bit early. Perhaps its just the cam being an MC1 rather than a stealth or such. It is still running standard heads so that is likely to be a factor as you've both said but I did notice that when the cam was changed, it had pocketed pistons which V8D thought might mean that it had slightly bigger valves from the factory - no idea on this though!

Looks like I might be in the market for some heads at some point soon then! I was actually thinking about supercharging it after Summer if I get the job i'm shooting for though i've not done much research into it yet - would bigger heads be a good idea before thinking about this or should I not bother?

Before any of you ask, I don't have any magic power figures in my head that i'm shooting for, i'm just doing it to enhance the car bit by bit both on the mechanical side and everything else...

[Meatball]

If your going to supercharge it i would leave the heads as they are,i think powers supercharged units were all fitted to standard cars anyway.

[thenick]

Well I haven't really decided whether I will or not yet as I would need to look into reliability etc. But if I do then I was thinking of maybe putting in some low comp pistons, lightening and balancing and running a bit higher than stock boost to achieve decent power but not too much so as to not blow up the gearbox..! To be honest though, I want to do a few other things before any of that such as handling/brakes/carpets etc so i'll probably cross the bridge when I come to it. For now though, is the general concensus that its running fine but has a head restriction?

I'll obviously find out for sure when I pick it up and see if it feels faster or slower than normal!

Edited by thenick on Tuesday 29th January 20:27

[GreenV8S]

238 bhp sounds a bit low, but I wouldn't put much faith on the exact numbers. However, the comment about peak power occurring below 5000 seems to imply that the shape of the power curve is wrong which is a little more worrying. Assuming the mixture and timing are right now, I guess that's because the engine isn't breathing very well. So either the CR is too low, it's got a very stumpy cam, or the cam is worn, or the intake or exhaust are restricted.

You seem to have ruled out induction problems already by measuring depression in the plenum. If you have a cat exhaust you can put a pressure gauge into the lambda sensor boss to make sure the back pressure isn't excessive downstream of the precats. If the blockage is in the precats themselves you would probably see the headers heating up under power.

[thenick]

the car currently runs the ACT decat stuff so there should be nothing but two cherrybombs between the engine and fresh air so I wouldn't have thought that there was anything blocking the exhaust... The intake also seems to be completely free flowing as much as the standard heads will allow.

The cam as has been said is an MC1, but has been in less than a year and has always been warmed up properly, not left to idle after startup, run on valvoline VR1 racing etc so unless it was a bad grind, I can't imagine it would have worn?? The timing and mixture have been verified as spot on by Dave and the only other thing that I can't be sure of is the cam timing as it was done by Dave Batty though i'm not sure if this could cause such a result? When you say the CR could be down, what do you mean exactly, what could cause this to happen and what does it mean in terms of lost beer tokens?

[That Daddy]

This may be nothing more than retarded cam timing i know its a fair bit of work to check but........go for the obvious.

[im]

thenick said:

...and torque/bhp are up from 180/125 to a slightly more respectable 295/238.

Are you talking about like-for-like figures here?

Taking the bhp figures only, the 180 looks low even for an at-the-wheels figure from a 4.5L whilst the 295 looks high even for an at-the-flywheel figure.

Edited by im on Wednesday 30th January 12:24

[thegman]

im said:

thenick said:

...and torque/bhp are up from 180/125 to a slightly more respectable 295/238.

Are you talking about like-for-like figures here?

Taking the bhp figures only, the 180 looks low even for an at-the-wheels__ figure from a 4.5L whilst the 295 looks high even for an __at-the-flywheel figure.

think thats the torque figures.

[350Matt]

Do a compression check first on all cylinders, might be worth trying to get some exhaust temperature measurements for each cylinder as well as that would show if all the injectors are firing correctly. Alternatively take a look at the plugs after some full load work

Then start looking at cam timing

Matt

[David H]

As above, plus post a plot of the power and torque curves up if they're available.

[im]

thegman said:

im said:

thenick said:

...and torque/bhp are up from 180/125 to a slightly more respectable 295/238.

Are you talking about like-for-like figures here?

Taking the bhp figures only, the 180 looks low even for an at-the-wheels__ figure from a 4.5L whilst the 295 looks high even for an __at-the-flywheel figure.

think thats the torque figures.

What, so the bhp has gone from 125 to 238 whilst the torque has gone from 180 to 295?

Something is wrong shirley...

[thenick]

Yeah well it turned out that two of the injectors weren't firing before hence why the power was down so low but that has been rectified and it is now running decent mixture and timing on all cylinders at 238bhp and 295torque. The issue is that Dave reckons that its having some trouble at the top end as its peaking early though as he isn't an expert with the RV8, he's not sure what its likely to be. He basically wanted to know if he should continue mapping it, or let me take it to a garage to have it looked at before he finishes the map. Power graphs are going to be sent to me via email asap so i'll get them up here as soon as I have them.

Incidently, if I was to take it to a TVR garage to have it looked at, does anyone know any good ones near Norfolk??

[spend]

You got the perfect answer from Rob (std LR heads) IMHO. You can fiddle & f@rt to the nth degree, but until you change them you are wasting time/money, really you should have got BV heads before anything else I reckon. Many of the induction mods (and various tweaks) are based upon the BV heads as std on 500's...

V8d, CRE, Power will all BV your heads or you can try & get some 2nd hand...

Dave

[Meatball]

Theres not much point changing just the heads alone, while its all stripped out fit an blended/ported inlet manifold and trumpet base should give you about 30bhp

[thenick]

Cheers Dave, that sounds like a good voice of reason... If it is just that there is a head restriction then that's fine and at least I can get Dave to finish the map and get it back on the road. I'll look into getting the heads done at some point soon, I just wanted to be sure that its working properly before it gets mapped. I'll give CRE and a couple of others a ring in a bit and will still post the power graph up to check before Dave finishes it though