Dissappointing RR results

[V7 SLR]

Finally got V7 to the rollers last week but it didn't go according to plan. I'm actually down on power from last year.

 

Spec last year:

 

VHPD engine with DVA head with 32.5mm inlets and 28.3mm exhaust valves (both sides up 1mm from standard), standard VHPD cams timed at 130/100, standard KV6 "swan neck" induction, 4-2-1 cat-less SLR exhaust, larger injectors.

 

Results:

 

204bhp on Emerald's old rollers. "Electric" throttle response and generally consistent "pull" throughout rev range.

 

Changes this year:

 

1227 cams timed to 130/110, Jenvey induction with DVA/Bernard Scouse airbox on 40mm trumpets.

 

Results:

 

193bhp and noticable loss of "urge" all over. Part throttle feels as powerful as it gets, in other words, press harder on the accelerator and nothing noticably better happens. Throttle response appears hesitant.

 

 

Observations:

 

My shimming technique obviously needs refining as the gaps are still too wide (some are 14 thou). I've asked DVA if he can supply a new set which I'll get on with grinding after this weekend's Irish trip. In addition I've noticed that most people with a DVA head/1227 cams/Jenvey's appear to be using 90mm trumpets, or longer. My whole induction length is now only about 2/3rds of what it used to be.

 

 

What to do?

 

Even if I sort out the shim gaps, re-time the cams and try some longer trumpets I stillcan't see me finding 30bhp. Any other clues please?

 

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[V7 SLR]

Forgot to mention, Karl (Emerald) had to take out loads of fuelling from last year's map. I put this down to the injectors being about half the distance from the head that they used to be but this is the only explanation I could think of.

 

Also, when the car went for the MoT it would have failed until I advanced the ignition 15 degrees at 2500rpm (I was trying a few different things, always returning to original before trying another change). If you rev the car out of gear and hold it, it "thrums" as though the mixture was weak. If you richen it up the "thrumming" goes away but so does the chances of it passing the MoT. Return it to original and advance the ignition and the "thrumming" goes away and all the figures become "passable".

 

Is this thrumming an indication of something wrong? The ignition map has consistent readings once you start to apply load to the engine, but the zero load figures are massively retarded by comparison.

 

As you can see, I'm just starting to understand what changes to the map do in the real world.

 

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[V7 SLR]

No-one with similar engine/experience got any comments? ☹️

 

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[tom7]

Nige,

 

I was with Oily on saturday morning and he did say that Emerald's new RR may be reading 10% or so under based on results gained from a known car.

Not much help on the tech stuff I'm afraid but may explain some of the difference.

 

Tom

[V7 SLR]

Interesting, but still a bit disappointing to drive. Maybe if I can sort out the noisy tappets and improve the throttle response it'll start to drive better.

 

Thanks for that though Tom.

 

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[Jason Plato]

I suspect most of us posted on se7ens list .........

 

Dave

[V7 SLR]

Trying to reach those that aren't on both Dave... or giving people a second chance.

 

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[Bob Corb]

It sounds like you've got several issues going on here...

 

Primarily the inlet wave tuning is now completely changed compared to last year. Shorting the inlet system so much will push the primary tuning peak further up in the rev range which may be good for an R500 or something capable of revving higher but perhaps not in the rev range which you operate in. What speeds were the maximum power points being achieved? Did it tail off previously whereas now it carries on?? 130 EMOP sounds very advanced too, I thought the std VHPD EMOP was 106 (or was it 108...?). Try borrowing a set of 90mm trumpets and a full remap.

 

If you forward me some power curves then I'll throw them into the master computer at work and see what falls out...I may need a few more details for the analysis though. (pls send to rcorbishley@cosworth-technology.co.uk not my home email on the link)

 

The thrumming is probably unstable combustion due to excessive ignition retard, overfuelling may help compensate but you really should put in more spark and close the air bleeds slightly. Not all engines take to having lots of retard at idle (big port heads with lowish tumble are the worst culprits).

 

BC

 

[oilyhands]

Bob,

 

The 130/100 refers to Lift at TDC in thou rather than lobe centre...

 

Oily

[Bob Corb]

I see....

 

one of these days I learn how engines work 😬

 

BC

[Bob Corb]

and to be more patient with the internet

 

Edited by - bob corb on 12 May 2003 23:10:39

[murph7355]

Could be talking out of my exhaust Nige, as ever, but I'm not convinced the shorter trumpets are the root cause - my car's OK on v.short trumpets and whilst not giving the power levels you're looking for, it gives slightly more than yours is now "showing" even with them (and 740 cams). I was under the impression it made more of a difference to the shape/positioning of curves rather than ultimate figures.

 

Oddly my initial impression over the first few lines of your post was that you can never take rr figures as a full and final measure...and then it was noted that Emerald have a new RR...A 10% margin of error probably puts you right where you should be given a few more minor tweaks you could make.

 

Of course the most important thing in your post is that it doesn't feel as srpitely as it did. If you know the shims aren't as good as they could be, then these'd be a good place to start.

 

Might it also be worth a full remap - and perhaps check your throttle linkage. I know it sounds daft, but mine's quite heavy (I like it this way) which goes a long way to making a difference. The R500 I had was soooooo much lighter purely on the throttle pedal - I found it much harder to drive smoothly as a consequence.

[V7 SLR]

Ooh, some contributors... excellent (and thanks).

 

1.We did do a full power run. I can't remember if it was still climbing. The logging facility was failing and resorted to interpolating. Karl is experimenting with different power supplies but hadn't got it right that day. Perhaps my power is low because it is still climbing past my max revs. I'm going to try longer trumpets. Perhaps they will bring the peak power down whereupon I'll see a noticable maximum which will give me a better feel for what's going on. My max revs are 8000 on the road but I'll push that a bit on the RR just to see where the curve starts to tail (8300rpm max).

 

2. The new Emerald rollers don't produce results in the same format as before so I wasn't convinced I could accurately compare them, therefore I didn't ask for the power curve. If anyone develops a way to compare the old with the new I'll email Karl and ask him for the file.

 

3. I'm going to re-shim. I am a fool and regularly grind them too small. I'm going to start with them a tad large this time. I still reckon my technique is amazing though. 😬

 

4. I shall play with the ignition map at no load just to see if I can increase the "blip" response and reduce the "thrumming" noises. Looking at the ignition map, the figures at these load sites are very much retarded compared with those at load site 1 and above. I'm not sure I fully understand why this might be. Can anyone help please? I had thought that if the ignition is "out" here, then it may be similarly out elsewhere but having looked at the map I don't think that's likely.

 

5. I've been offered the loan of some longer trumpets, so am now saving money for another RR session where I can try these. I'd like to go back to Emerald though because I like them and trust them. Karl was VERY thorough on Wednesday. I think he checked every single load site suring the day (hence my confusion over the ignition map at idle).

 

6. Despite everyone's advice, I didn't check my throttle linkage before the mapping session but Karl (bless him) did and we (Mick, Karl and I) spent a good deal of time getting right. I had thought that I wouldn't like the Jenvey "lever" because I used to have a 1/4 cam on my KV6 TB's which gives consistent feel across all throttle openings. The lever shouldn't give such consistency, but in practice I'm finding it to be fine. Karl and I also set the throttle balance. It's now absolutely bang on.

 

Thanks for the contributions guys. I find the whole issue fascinating although I wish it was a bit easier.

 

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[Peter Carmichael]

Regarding point 4.

 

The retarded settings at idle are to give a good base idle from which rock solid idle stability can be achieved using extra advance as required.

 

All ignition and fuel figures are interpolated. As soon as the throttle moves away from the throttle stop, the ECU recognises this and starts interpolating towards the load site 1 figure. Usually LS1 has a lot of advance and this climb is sharp enough to give electric throttle response. The problem is not there.

 

The problem is equally not to do with the putative 10% change on the Emerald rolling road. It possibly has more to do with the acceleration runs taking much longer because the road has a load cell expecting to soak up 400+ horsepower. Power runs should not take over a minute as it is difficult to maintain temperatures. Emerald have this in hand.

 

As for being different on the road, this is the real clue to your problem. For some reason the engine is not making power. The usual culprit is cam timing rather than shimming although the two are interrelated. This is the problem with lift at TDC cam timing. If the shimming is wrong the timing shifts.

 

So two things to look at. How do you keep getting the shimming so wrong? Usually I can just shuffle the shims I have around and at worst I end up grinding a couple - almost impossible to get them all out.

[V7 SLR]

I've just spoken to Miraz. He has emailed a copy of his ignition map to me which plainly doesn't have low advance numbers at LS0 compared to LS1... and then he told me that his ECU doesn't have idle stability control as per the M3DK.

 

And then I read what Peter wrote above which perfectly explains the idle stability control. Thanks to both. Karl spent ages on my car and I'm convinced he did as good a job as was possible with that car. I wasn't calling into question anything he did but it's nice to know some of my observations and questions about what he did are proven wrong. I watched him alter the ignition and injection settings to get best lambda and then best power. There's no better scientific way to achieve best results. AND he did every single load/speed site... one at a time. Very thorough.

 

I'm encouraged by your assertion that cam timing is most often the culprit. As my shims are so laughably wrong, you are right that the cam timing will be out too. I'll put that right and return. Why do I get it wrong so often? It'd take ages to explain my technique but it's obviously wrong. I'll return to the way DVA originally showed me I think. Hopefully I'll be able to jiggle a few around, but I reckon I'll need a complete set this time or next so I've asked DVA if he can send me a set. Cheque waiting.

 

Emerald's possible 10% discrepancy doesn't really explain why Mick Smith's engine gave over 10bhp more than mine given the similar specs (to 8000rpm) so I'd kind of ruled that out.... also as you say, the feel on the road speaks volumes even if my backside isn't calibrated enough to give absolute figures (howabout 42/40/36..?).

 

Thanks.

 

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[murph7355]

With so much hand fettling involved in these things, is 10bhp such a discrepency?

 

Again, looking at engines of similar specs to my own (a while ago), the differences in power were sometimes quite a bit more than this, and I guess the difference between "best" and "worst" could easily have been more like 20bhp (mine fell in neither camp).

 

I was a bit mis' at first when I saw this, but now I don't really care too much.

 

No matter how much I try and kid myself, my arse isn't so attuned that I can tell the difference between 200 and 210 peak power. And similarly I've been of the opinion for a while that anything over 200bhp doesn't make the car *that* much quicker, the overall characteristics of the engine and chassis being of significantly greater importance.

 

[V7 SLR]

I think you're missing an important element of the discussion. V7 is down on power. It is obvious when driving it, therefore it is down on a LOT of power.

 

Some people with my engine spec see more than 230bhp. I saw just over 190bhp. That's quite a discrepancy which can be partly explained by different RR's but doesn't explain the fact that it is slow to respond to quick throttle openings and has obvious (i.e. you can feel them) flat spots in the acceleration curve.

 

There are also obvious shortcomings in my building of the engine, particularly in the shims which, as Peter explained, will affect the cam timing which in turn will lead to the observed results.

 

Anyway, DVA hand fettling is more accurate than any machine found at Rover. 😬

 

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[Tony Martyr]

Nigel,

Your readings are within the plus/minus error band of this type of RR test and the methodology used, if reasonable correlation is required, is crap. So don't read too much into the mumbers. Your subjective opinion as to the feel and use of your calibrated backside are probably much more use.

The number I would like to see would be exhaust back-pressure measured before the silencer can. If you have improved air in but increased exhaust bp in doing so you may suffer a net decrease in peak power. The curve shape comparison would be useful here

I am dealing with this problem at an Motor sport test site at present and the more we try out differing settings and tube configuations the more unexpected effects we find. (which is why I will not be at the monthy pub meeting tomorrow night with the rest of the gang.)

[Bob Corb]

Nigel

 

I was speaking to Miraz last night about inlet tuning, his engine has a DVA VVC head with 32.5 mm inlets, 1227 cams and Jenvey throttle bodies. On the rolls it makes 240BHP at 8200rpm. The throttles are spaced off the head by 19mm and he's got 120mm trumpets too. Thats a huge change copared to yours and will tune totally differently. This is backed up by the fact that you were pulling so much fuel out of your map.

 

BC

[Jason Plato]

Whilst I see that your are 69mm shorter in trumpet length than the "norm" - that being 19mm spacers + 90mm trumpets .I dont think this is the the only possible issue .

When I did a back to back trumpet test at "good old " Emerald with my 1600K on K16 head , my 90 mm trumpets made 206bhp , we changed to 130mm trumpets + 19mm spacers trumpets and it produced 210bhp . BUT the gains were in the mid range where we gained 24bhp and 24lb torque . Note these gains were as a result of the 2 dips at 4500 and 5500 being effectivly inverted with no losses .

We then put the 130mm trumpets + 19mm spacers onto Peter C's engine - it made 250bhp as before with +/- 2 bhp through the entire range .

Now my gains may have been as a result of either less than optimum cam timing for a 1600 ( 130/110) as opposed to much of the development having been done on 1800's . Or PC's timing was optimum , or the optimum tuned length for a 1800 on VVc head is around 109mm on DTHTB's ??

 

There have been several 1800 engines making 235-240bhp on 90mm trumpets + 19mm spacers . I wonder if 120mm are actually required - It would have been good to have done a back to back test with Miraz's engine too ....

 

I would like to try some 160mm trumpets to see what happens - but thats another story .

 

I would consider doing - as Rob Walker suggested , a leakdown test and compression test first .

 

My 90mm trumpets are boxed and ready to post if you need them for a test .

 

Dave

[Jason Plato]

I just noted that you also sense flat spots whilst driving - this could be the timing . Did you see 2 dips on the power graph ??

 

These have been flattened on other 1800 engines with the cam timing .

 

Dave

[Miraz]

Dave - I'll be fitting the full spec engine sometime in the next couple of weeks and taking it down to Powerstation to be mapped - it would be interesting to do some back to back tests for different induction systems at the same time.

 

Miraz

[Jason Plato]

Miraz ,

 

Let me know when you are there , I can bring along my 90 mm trumpets and my 120mm's .

 

Would be very interesting .

 

Dave

[V7 SLR]

Dave, the shims are so far out that PC rightly points out my cam timing will be pretty far out too. This is consistent with flat spots and poor throttle response. I'm going to sort that out as soon as I get back from Ireland (this weekend) and then I'll arrange another RR session at Emerald at which time I will gratefully borrow your trumpets.

 

I feel that correct shims and cam timing ought to give me the power and correct trumpets will place that power where I need it (below 8000rpm). I'm intrigued as to whether 120mm or longer trumpets will help with this placement but as long as I can get the peak down to below 8000rpm I'll stick with the shortest that achieve that. Hopefully this means I am able to retain the airbox, although to get the power where I want it means I'll investigate whatever mechanisms are necessary.

 

My current engine is similar in spec to the one Miraz and countless others have RR'd at around 230bhp so I'm confident (again. I lost my confidence and interest a bit last week) that I can achieve it too.

 

Thanks.

 

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