Low points in Ve table graph.

[jessejames09]

I've just finished getting the top end of my ve table tuned,and I've got area around 5400-5800rpm@90-95-100 cells,that isn't flowing well. It spikes back up around 6000rpm,and I've got fuel cut set at 6250 ,so not sure if the spike is from that .
Could someone shed some light as to what it may be please. Have done the following to the holden series 2vp block,and vr heads.
Stage 3 Cnc port to as much as standard vr valves will flow,polished chamber, ex ports etc.
Mace over size throttlebody ,67mm ?
Portmatched intake,bell mouth removed.
Standard 19.5lb semiems injectors
1.7:1 yellaterra rockers
Cam lift 506 in&ex 282 duration @50 . 110 centerline,have advanced it up to 106 centerline.
3 into 1 collector,15/8 inch primarys finish under drivers seat 2.5 inch exhaust, 2 into 1 tail pipe.
I'm only running 8.5:1 compression ratio as I've got plans to forced air induce it at some stage,and I'll dial the cam back 110 center line when I do.
So from an experts opinion, is it from the cam advanced to much,or have my heads just flatlined at that rpm ?
Injectors to maybey ,I am maxing them out but they still given me fuel ....

[Charlescrown]

Post a log and your bin file.

[vlad01]

Damn! those heads are mint! I've never seen CNC Buick heads before, are you able to share the info on them?

As for the VE, that's pretty normal on these with big cams, the bigger the durations, that more you get these double peaks. It's from the intake/exhaust coming in and out of resonance at certain rpms. The Formula Holden engines do the same as the have a similarly big cam and tuned headers and stock intake.


EDIT:

Also, are you sure the cam specs are not the advertised duration instead of the 50 thou? 282 at 50 thou is a huge cam and it should rev out north of 7 to 7.5k and need heavy normally triple springs. What I see there and the comp doesn't reflect a typical choice for such a cam spec.

I would have gone a higher comp even with boost if that cam spec is correct. Would be pretty lazy otherwise.

Just to give you an idea, specs of 262 deg at 50 thou, 303 advertised, 106 lsa and 102 center with 550 ish lift on both needs 11-11.5 comp on 98 fuel NA and makes around the 350-360hp mark at 6800-7000 with heads similar job to that. On boost, prob high 9s or 10 comp would be ideal. Less than that it will be lazy and leave a lot of power on the table.

[vlad01]

Here is the Formula VE that I ported to 12P some years ago from an original BIN from the series.

just FYI, despite common saying that peak VE = peak torque, it's a myth. I found on the dyno it to almost always be untrue. Yes, sometimes the torque curve can have a similar shape to the VE, I found most often it doesn't and when it does, the peaks in torque are miles off from the peaks in VE. So a wonky VE does not at all mean a wonky or bad torque and power curve. In fact, the bigger the cam, the more wonky VE and torque curves can get, especially with highly tuned exhaust and intake as you increase peaks with good tuning but always create troughs elsewhere.

This is why OEM cams have often very wide LSAs, it smooths the curve and improves emissions and sometimes efficiency( best at low speeds) but sacrifices overall performance. I wouldn't focus too much on the oddity of the VE table shapes, the VE is what the engine needs, if it;s spiky and that's what it likes, let it have it. Trying to smooth it out makes those engines run worse and get lean and rich patches where it's been smoothed.

All my engines are tuned with the VE as accurately as possible over long and repetitive logging and the spikes a show of good data integration time.

Screenshot 2024-05-12 232647.png (31.52 KiB) Viewed 453 times

Here is a stock VR engine, note how the spikes are well defined in pattern, the stock factory tune it just an approximation to fit 100s of 1000s of cars so smoothing helps them average out better over the production run, where individual tuning, it's best to let it have what it wants.

Screenshot 2024-05-12 235259.png (32.93 KiB) Viewed 451 times

[jessejames09]

Thank you for the detailed information as to what I'm spose to be looking at,which is some very interesting information.
The heads where done by Hartleys motor sports here in NZ ,who are based in Palmerstin north. I'm running their super 6 class speedway combo ,in which they didn't give me a cam spec card as they want to keep it secret I guess. So when I dialed the cam in ,(2 years ago) going from memory on the degree wheel,so have probably got advertised duration wrong . 506 lift at the valves for sure ...I do remember that ! . The cam is good for 6500 rpm from their description, so low on compression is why I've advanced it by 4 deg. It's a bit lazy until 3000rpm ,but it goes alrite,thank f its behind a manual or I'd be sorry . I got shafted with piston height when I brought them,and the guy wouldn't accept a return so I got stuck with them, or I'd be running a preferred 9.5 :1 . Still managed 160psi in the chamber dailing it in at 106 centerline......it will do till I boost it .
Re the Ve table ,its very intriguing how it drops so quick at that rpm ,and like you say it still feels like it's pulling in those cells . My thoughts seeing it flow again at 5800-6000k ,thought something was wrong ! . Thank you for the clarification of how it works ,was thinking the bpw was maxing the fuel flow out or something, but thought I'd ask before playing with stuff that's probably set correct .

[vlad01]

They are nice heads indeed! I'm always jealous of you NZ guys, you always have all the good engine stuff and companies and have good support for the Buick. Over here, if it ain't LS or Barra, they aren't interested in helping you most of the time.

Given the rpm range of the cam, I would say the 280 odd deg is probably the advertised and the 50 thou might be more like 230-240 which would make much more sense from all the other stuff you have provided info and pics on.

What pistons did you use? As far as the only pistons you can get for these engines here are the Hypertec stock replacement ones, or the only performance piston is the Mahle Motor sport "ACL race series" clone forged pistons. They give a 10:1 comp in most engines out of the box.

For a future project of mine, I will need custom pistons, same as the Mahle ones but with a smaller dish and full floating pin as I want to use after market Carrilo rods just so I can have Carr bolts I don't trust ARP with their bad batches over the years.


Here is the dyno results vs the VE for that engine.

Not much correlation between the two, and even the spark map didn't line up with any of them either.

Screenshot 2024-05-12 235259.png (32.93 KiB) Viewed 391 times

vlad dyno_zps4wmqtxuy.png (199.15 KiB) Viewed 391 times

[jessejames09]

Wow those figures are definitely not what I'd think you would see ,especially how the torque curve is all over the place while on the increase. Nice squeeze of HP from the tune though ,very cool .
I'm just road tuning at the moment, getting it to run nice and fuel efficient which after a year ,finally got it dailed in. I have a little flat spot when crusiing and hit throttle lean spike issue I have to work out but other than that it's running sweet. I keep cranking my AE delta manifold fuel up,which worked to a point before the rpm AE increase kicks in,but it didn't solve it. Any more and i lost throttle response and still have the hesitation. l check vthe brake check valve before I go further I think.
Re the heads....yes very lucky to have Hartleys close by,and as he had a batch of other buick heads to do,he only charged $1700.00,totally worth the money,and good team to deal with too.

[jessejames09]

Oh and yes forgot to mention that I'm just using the hypertec pistons . When buying them I was told I was buying vp pistons,which one would think be 8.5:1 right ? Well having plans of milling block and heads ,smaller VR chamber,60 0ver pistons, that I'd get at least around 9.0:1 . Well they worked out to be 8.0:1 .I asked for a pistin/pin height when purchasing ,he assured me they were what I wanted ,then turned his back on me after I received them. I was eyeing up some JE pistons feom the states ,which were 9.0:1 judging by the piston height measurements,but they didn't have 60 over,and they the thinner rings .
The speedway guys run 80 over bore and use short skirt triumph pistons at 10:1 I didn't ask what triumph motor ...can find out though.

[vlad01]

My other mild hot engine's torque curve is wavy as hell, this stock engine is very smooth in the curve by comparison. The hot engine has a 109 LSA and a decent amount of overlap which all make the curves go wonky and the centerline is 114 or there abouts. Only 212 duration and 470 lift, but makes about 140 kw (close to 190hp I think?) at the tyres. It has the last ACL race series pistons as a Nason brand, same specs as the Mahle ones but cast and slotted oil ring land, but it has the high comp and accumulator groove just like the original ACL and Mahle pistons of the day. Not sure on the exact comp, but it was shy of 10:1

It really needed a bigger cam for the rest of the combo in hind sight, after playing with these engines for a long time, I found they really love a good cam, the bigger the better as long as the rest of the engine combo is built to suit, high comp, good competition pacemaker headers and good corner CAI air box.

It's common myth that because it's a V6 it wants no more than a mild or small cam, but in reality these engines respond to cams extremely well and much better than other common engines, I think the myth comes from ecotecs, they are pretty mediocre I found for various reasons.


For the hypertech pistons, the VR ones have a higher comp height but larger dish, for better squish, the height difference and the dish are so that the comp is higher overall at 9:1.

They say VR head have a smaller chamber, but I found no visible difference and I think it's only a few single CCs anyway so it's bugger all towards the comp.

Your CNC heads on the other hand, I can tell you for sure that the CCs are wayy more than stock, so that would explain your low comp.

This is the issue I have if I want to get a Formula Holden based build, none of the "high comp" pistons will work due to the reworked and larger chamber and I'll end up with inadequate comp to suit the cam.

But since custom pistons are a given these days, it's basically an non issue.

[jessejames09]

Looking back I should have got the VR pistons. I had the block milled 16thou from the last build ,and hartleys milled the heads 40thou to get the chamber back to 42cc,same as stock. I'm using some 80thou Teflon intake gaskets so the manifold fits properly, which wasn't a problem. Things we learn as build motors ,il know for next time. I'm tossing up between the raptor kit ,or turbo ,see how much cash I have in the near future and make a call when the time comes.
It's my daily driver that I have in a hilux ,so I'm not looking at a drag motor ,just enough to smoke a Ford ranger