Split: Why doesnt drunkenalan's car make more power!!! little bump

2 inch is'nt too bad Alan, but the internals could be breaking up...I've seen that a lot on Scorpion in the early days. Is there a fairly strong pulse coming from the tailpipe on idle and/or with the revs increased?

I walked past the back of a hillclimb car on the rollers many months ago, the tuner was struggling to get any power out of it whilst mapping. As I walked by all I felt was a light pressure rather than a strong blow (ooh err!). I suggested there maybe an exhaust issue/blockage..."no no it cant be that, it's a straight through system" was the reply. After a gutless run on the hill they changed the exhaust and found the missing power...odd that.

That raceland manifold looks ok in terms of flow, the lengths are a bit short but should be ok for the use, though the outlet looks massive...maybe just the pic.

Whilst the cam timing may have been swung the sweet spot may have been missed. I set the cam timing up on the bench when I did the last hillclimb engine by simply giving the inlet a touch more lift than the exhaust by feel accross the valves.. I just needed a quick base setting to run the engine in on. On the dyno it was down on power. Setting up the dial gauge to find a true value between inlet and exhaust picked up the missing 20hp.

You need to find the true tdc with a dial gauge down the plug hole...I have an adaptor for this which makes life easy but you can do it with a long extension on a dti.

Ignor the front cover marks as these can be out with the belt cover floating around... the flywheel is much better, but you need that true reading. You then need to set up the dti to read off the inlet bucket, turn the engine forward from the tdc position and note the lift when it stops moving...that will tell you what it was at tdc. Do the same on the exhaust but turn the engine the other way (after re-setting the true tdc position before or course).

Forget any manufactures settings, (tonyb found 14hp by reducing the inlet lift @ tdc from the Schrick setting after I hounded him enough, and I've seen it many times on the dyno too) you need to see around 15thou more lift on the inlet than the exhaust..10-12 is fine, 16-17 ok, 18-20 getting too much. The actual figure..2, 3mm (0.080-0.120) is irrelivent. Advancing and retarding based on the markings/arrow on the cam pully is telling you nothing... you could be advancing and/or retarding from already advanced or retarded positions...i.e the keyway could be out... its the relationship between the inlet & exhaust lift that you need to establish..that will tell you true advance or retard.

As Mike has said above, many engines that have proven power use std type plenums.. some up to 160+hp with wild cams... much wilder than yours... irrispective of the numbers, they dont flatten out on the power curves. There is a but though... most are smaller in capacity, apart from Mike Flyn's Kamai replica, I think thats a 2.1 with a 95.5 crank...and a 282 cam on the same valve size as yours, on a plenum too... think that made 160+ @ around mid 5K...Mike?...so it's not lacking too much.

The old slick 50/road saloon spec engines make 155-165hp (Sam Fish's around the lower figure, Chris Eyre's old steed and others up at the higher end) @ around 6,700-7k on plenums with 296-304 degree cams and restricted exhaust manifolds (ported but still way off optimum for the spec) from 1800cc.

A bigger capacity engine needs big breathing... they will always produce decent power lower in the range and run out of air capacity as the revs build and sometimes show the same or less peak power...tape over one nostrel and half of an olympic sprinters mouth and see if he can still run the 400 metres in the same time, dispite his chunky legs getting him off the line the same.

Std plenums flow very well, a ported head on a std plenum doesnt. Porting the runners will help bring most of the flow back, in fact withing a couple of cfm of a bare head up to around .430 lift from the tests I've done. From .450 they start to restrict flow a fair bit, but up to that point they will allow good cylinder filling. Yours is around .460 (11.7mm) depending on how good a copy, so just over the ideal zone, but no big issue there. It will be worth measuring the total lift while you have a dti to hand, just to make sure the lift is close to the above.

Your compression ratio is close to the cam spec too... a touch down on ideal but no biggie.. it's not causing the problem you have.

Throttle body will be fine too... taking them off completly gains 2cfm over a bare manifold.

The exhaust is easy to check both on idle and with the revs picked up... dont burn yr hand!... not much pressure coming out...not much power with it.. a simple and easy/obvious fix.

Id go with the cam timing next, it's a pain doing it that way without the right gear, but the only way to get the inlet/exhaust relationship right. In a worse case you'll at least have the cam timing right for the future.

 

I am very sure any change in characteristic would have been picked up during the cam timing sweep. This was moved in an DOE type experiment adv/ret 11 in 3 or 2 deg steps along with engine control changes. So what you are suggesting regarding using a DTI gauge for static timing would have been picked up during the cam timing sweep. I could have been more ambitious and done 1 deg steps, but the issues with what I strongly believe to be manifold pressure oscillations were still present.
At each step the calibration was adjusted to ensure the engine was running MBT/LBT for the air charge. At any rate the oscillations in torque were still present at higher rpm, though the torque shape was most defiantly altered.
At this stage there is not a "missing 20hp" but a distinct wobble in torque past 4500rpm. This is what must be understood if the engine is to achieve more performance.

The front cover marks are good enough for the method that was chosen during the cam/calibration sweeps.
No need to go over what was already done, please read my thoughts in preceding posts after testing.

We are not looking at any manufacturer settings ( it is a custom engine after all). Study the torque profiles for this engine and then comment what is driving the shape. Forget other engines for the while.
You do need to be a bit more understanding regarding the effort and time spent on this engine by both myself and Alan and the fact that the GS guys allowed us to spend upwards of an 1hr trying to get this engine to perform considerably better at WOT at no extra charge. Please do consider that.
In addition to the sweeping on cam settings, the engine was set to TDC ( plug out and long screwdriver in) and the cam was moved a plus or minus a tooth and swept through the vernier steps. This was done on the road, along with calibration iterations. The engine character did change but the vernier settings seem to be at the end stops with these tooth step changes. Without the dyno or G meter at the time we went by feel.
On the dyno further work was done to the cam position and I can confirm the current postion is the nominal postion. However the real problem are the torque occilations occuring after 4500rpm. Regardless of what is done to cam tgiming this still occurs.
I am sure we can achieve more optimisation as you suggested, by either using a DTI gauge and a crank angle timing disc, but this will only be benficial if the torque oscillations, post 4500rpm go away.
This takes great patience and time to carry out these adjustrment and they are based on many informed judgements.

As I have been involved in both Mike H's and Alan's engines both from a drivability and power and torque perspective and can relate the numbers generated at Garage Streamline to vehicle feel. I would expect Alan's engine to achieve on these Dyno Dyanmic rollers ~150lbft @4800rpm and ~160ishPS@6000rpm and 110lbft of torque @7000rpm.
Currently this will not occur until the wobble and steps in the torque still occur.
Other engines making whatever and where ever are not of any interest unless there is further data and correlation going on to relate to this specific problem. Again that would take considerable time to set up and would result in information that I already know i.e. Alan's car has a problem!

The runners are not the issue here regarding the pressure waves that are pulsing in the std PB plenum. This is a dynamic issue that requires a bit more understanding to solve.

Yes, I agree, this is issue is not caused by CR and even though as you say it could have been a but more, you would still have the intake pressure wave stuff creeping in at higher rpm and reducing breathing as each runner air column is agitated.
2 stage throttles on these are have similar area reductions as VR6 and ABF units.

The camshaft timing can be rebasedlined when the plenum is rectified to tip the torque curve as required. We have not got to that stage as the torque oscillations demonstrated in the graphs need to be fixed first.


While I am happy for opinions on this subject, though I did not ask for any advice, please understand these points:

• Testing on these projects are done to get the maximum response of the powertrain be it an 8v, 16v, 20v, VR6 or 800PS Skyline/Supra, the ethos is the same. WOT is not everything it is how the engine ramps to WOT loads from anywhere!
• Every effort within reason is attempted to achieve the above.
• Drive character at lower loads must be optimised as best as possible or any request of the owner if it is within reason.
• Expertise used is not that of a novice.
• Dyno time, the the expertise to operate and run it, is expensive and is used when validation or investigation is required.
• Setting up test clinics and driving distances to pre optimise vehicles are very time consuming and not necessarily profitable to myself, but are done to assist some enthusiasts of the club and the general enthusiast knowledge.

My experience has been the suggestion you gave regarding cam timing are valid

• If the base engine has a matched dress kit.
• You discover you can tip an LBT/MBT torque curve after optimising that last 3lbft to achieve you advertised power peak.

These are tricks I would pull out but not when there is a fundamental problem that is being worked on.

 

If you think you can get away with the noise - pull the back box off and give it a try? The Scorpion box I had wasn't a straight through though...

 

That is an odd design of exhaust manifold. The secondaries look half the length of the primaries. It is normally the other way round on conventional 4-2-1 manifolds. Even OEM ones are nowt like that.

If there are pressure fluctuations in the inlet plenum could they not be caused by exhaust reversion in the scavenging phase? Every engine once modified substantially is going to have it's own unique characteristics and it could just be a mismatch and clash of specifications and components.

Nothing relevant in this post from the other thread with regard to resonance and dampening the intake system?
http://www.clubgti.com/forum/showpost.php?p=2125016&postcount=72

 

The design tends towards a 4-1 sort of, but not something I would worry about at this stage.

Exhaust reversion can occur at slow speeds and on cam overlap, not helped by equal matched exhaust ports and big cams. Scavenging will occur at high engine speeds when the exhaust path develops sufficient negative pressure at the closing exhaust valve, to start removing residual combustion gas for the next stroke. The intensity of the this "negative supercharging" can be tuned via exhaust lengths. The opposite effect " natural supercharging" can occur the intake system based on tuned running lengths and plenum volume based on rpm.
Yes each engine does have its own character, however with the ability to control certain aspects of that character via mapping or adjustable camshaft vernier a consistent torque curve should result. From here the dress kit items could be improved or replaced to fine tune the engine to produce power and torque that could be a maximum.

No that was the posters attempt to school us in airbox airhorns and why we should keep them! Looks like he did not use search and find the 16v AIS thread!

 

i think that there is a pretty strong flow at idle!! i get a vid of the palm bush getting its morning blast of HC's!! the system is old and im searching for a 16v exhaust to be sure!

the outlet of the manifold is design for a cat or a decat, its a 2 inch pipe see below


as eddie said we did sweep the cam across the vernier range in small increments, so i would hope we would have found a sweet spot, I will re check the cam and re time it, have you ever come across autosprint products?? the cam will always have a ? mark over it for me, until i see the kind of figures that the engine should make!!

Mike' engine is a TSR, so we have many components that are the same or similar. Mike is a true 2.1 where mine is a big 2.0, they both have shed heads altho i think mike' has the 40.5 inlets!! other than that they are almost the same!!

thanks for your advice it is all welcome, the engine seems to have a the components to make bigger figures but for some reason it just wont..

On the list of things to do...

custom inlet manifold - it will be pb runners with a custom plenum.
find a bigger flowing exhaust - i have a supersprint B/box already
try an get a similar spec cam to try at least!!

 

I think everyone is just really interested to see you get to the bottom this Alan. The build has been an interesting one that lots of folk have enjoyed seeing it come together.

I wonder about the cam grind too. It is not unknown for them to be set wrong when creating the lobe offset phasing.
That exhaust does look like a real step down in diameter from the manifold unless the warp is deceptively thick. It could be creating an unwanted pressure pulse back up the manifold.

Eddie, these are just people responding with ideas to bounce around the place. It is not meant as personal, the folk making their suggestions and adding ideas to the mix are well aware of the time and effort it takes to do this sort thing. Some also have a lot of experience and will have seen odd things too that may be useful to others.
If these are discounted then there is no point starting a thread asking why, when it is absolutely known what the problem is.....

I am sure you will get to the bottom of it either way.

 

I am happy for experience and expertise to be channelled into ideas that relate to what we are talking about here i.e. this engine's inability to produce consistent torque post 4500 rpm when running an optimised engine calibration.
The odd thing - how choppy the torque is as the revs become higher. This engine has been driven and it needs to sustain the kick it has on launch to around 4900 rpm and decay slowly to 7000 rpm. I am confident this engine can deliver the WOT torque curve as described.


Alan on myself are on top the issue.

 

As per Herr Doktor Danster, I'm sure that yourself and Doktor SuperEntwickler Toyotek will sort this out.

I'm really interested to see the results of your plenum experiments... keep the drawings in case it gets a big gain, as I'll be looking for one as well!

Eddie rang me last night, and I said on the phone, I can't help wondering if there's a partial obstruction in the exhaust, causing some sort of reflected interference pulse back up the exhaust. I used the example of a high school physics wave tank experiment, where the waves hit a partial obstruction, and that causes waves to flow back (in this case, exhaust gas pulses) and then form either a constructive or destructive interference pattern.

I'm suggesting that this could be the source of the pulsing you're seeing at the MAP sensor, and more-so when the partially restricted (in theory) exhaust is flowing at capacity (at high RPM) but of course that relies on the cam overlap to feed the pulse back up the inlet tract. I'm not enough of an engineer (even a keyboard engineer ) to make an educated guess at whether that's feasible on the overlap of your cam.

All very well in theory, but it could be I'm talking total rubbish in practice. In your shoes though, I'd be scouring the classifieds for a used 2" Jetex or Supersprint system to chuck on there. I think 2.5" is too big for your application, and it'll cost you bottom end driveability.

 

I will draw the manifold up mike!! and hopefully get some decent assembly photos too.

Im scouring believe me, if anyone sees a decent exhaust at a reasonable price, let me know please!!

 

While this thread is still up I'd just say have a look at the exhaust system. When I first started upgrading my slick 50 spec motor I added twin 45's and mapped ignition and a 4 branch mainfold (D spec head and Scrick 304 already on it) and I kept the longlife 2" S/S twin box system.

I took it on the road and it felt strong enough, up on what it was before. Vince ran it up on the dyno and rang me, we had about 150bhp, that just wasn't right. He had played about a bit with the jetting and cam timming and that is about where it wanted to be.

I rand him back up after a think and told him to keep it on the road and I took an Ashley rally system up, 2.25mm dia, still twin silencer (and about half a ton in weight). We ran it back up and got 160bhp which was closer to what I had expected.

All I noticed on the Longlife system (cutom made for the car) was that the bends were not properly formed and just didn't look right and that's why we changed it and found 10bhp. There was nothing wrong with the silencers as far as I was aware.

I would certainly drop the system off and (noise permitting) run it up just to see if you find and significant power as it's easy to do and could make a big difference as it's the only thing you won't have had a look in to.

 

I have actually enjoyed reading this thread. A little educated and slightly heated discussion generally makes for a good read.

Regarding engines, no-one is right on everything. There could be many reasons why Alans engine is not putting out the numbers / shapes many were expecting.

If we dig beyond the tone above, there are some real valid points raised above, getting the mechanical set-up of the base engine checked and double checked as accurately as possible - nothing is going to work to 100% of it's potential without this - and also the strange wobble in the torque curve post 4.5k.

Not being an engine "pro" by any means, but having a general understanding of tuned engines, that wobble looks like issues with destructive harmonics, my money would be that it is being caused by exhaust back pressure or cam selection. Never heard of the brand being used tbh... (but that could just be my ignorance of 8v's)

 

I do agree with this, and this aspect has a part to play in all good debates. However I am very nervous when highly knowledgeable folk are getting prickly with each other, as there is too much at stake.

 

Any chance of editing thread title and removing the question mark. It is a statement and explanation, not a question.

 

I hope this thread doesn't get deleted and that two very knowledgable people don't have a major bust up.

This thread would be more than useful for many people with 2.1 (ok 2042! like Alan's) and possibly folk with engines with this same issue or as a gudiance to possibly other issues with engine tuning, and that he can thread this path with quite some success so that all people following along myself included don't have to spend time and moneyto come to the same outcome as Alan.

Not everyone is a pro and and people sometimes get things wrong. But with knowledge comes power and with power comes responsibilty! I don't think I've nicked that from a film!lol

Fingers crossed things can be resolved and we can all enjoy the long, winding and sometimes tedious path Alan will be driving to get to a engine/power nirvana! So that others can get there and enjoy it to.

It's sometimes good to have aplace where ideas and problems can be bounced around and solved amongst friends where none of us will hold against anyone and can be chalked up to experience by which this forum contains a lot of wealth in.

Right enough of the soppy crap! Let's hope and help (when needed) Alan's power problem!

 

Another one to look out for is the front pulley,ive seen as much as 6 deg on a worn front pulley as the rubber damper wears with age.

 

Ok Dan

 

unhappy with tones one here?,i havent even been on,

 

http://img.photobucket.com/albums/v343/drunkenalan/utf-8BVklERU8wMDAyLjNncA.mp4

vid from cold start

thanks BenS

 

No yr wrong... that wont make any difference!

Sorry. forgot myself then. Thats one of the main points I was trying to make... it's all too easy to asume the obvious has to be right, but thats not always the case, these engines are getting on now and basic things like covers, pulleys and several re-builds under their belt start to move the manufactures goalposts and the baselines we look at.

Good point on the pulley... I was just kidding with the wrong thing...