Wowzers. Is that really all they do? Agree with the torque fluctuation, that could probably be improved slightly - however - that is MBT and removing or adding any more moved the whole map equally, with no more obvious gains to be seen. Optimising the fuel map further may also make a slight different but it was +- 0.2 AFR WOT across the band. I'm told it has the following: Race Pistons - No idea on compression ratio - judging by the timing I can run not very high. Head gas flowed, skimmed, ported & polished - no idea to what standard this has been done. Valves reground and milled to remove bulky head stem - Is this common on these? So assuming what I'm getting is typical, where can more gains be found? Thanks very much for your help btw, very kind, I appreciate it.
It's far from typical...they'll do better than that with that spec when they have the right parts/build. Even decent road engines don't like much over 28 degrees full advance with around 11:1. Ported and "polished" usually indicates more of the latter and not much material removal. Id certainly check the cam timing to start with, then go looking inside for the missing ponies.
When you say "far from typical", when an engine of the same spec and controls is tested on two Dyno Dynamics dynos, this gives persuasive evidence that the engines are similar. 28 of ignition timing at ? rpm or range would be MBT as a general statement - but the compression is not known. i.e. I would not expect 28 for spark advance at say 1500rpm and at WOT! Also the fuel octane and best torque combustion mixture would influence the burn rate thus timing. I agree if the camshaft is sync'd in an less than "optimal position" then the engine character and torque profile maybe still in the left of the plot and the mapping was just done to match that air charge. That is assuming that the OP did not take that into consideration which might not be the case. It could also be the car accelerates in the real world 'just like typical' and the method of data acquisition of power and torque is right and typical for this type of machine.
All said and done it drives very well, pleasantly surprised me on the road test. Cam timing will be checked next should the customer wish to.
With the trace you displayed it would have surprised me if you said it did not . Good work there with getting the torque to shift to the right .
Whilst a nice try Im not going down this road again..though I'll clear a couple of things up.. I did state to help the o.p the 28 degrees of advance to be at "full" advance...which normally happens from "around" 3,500rpm onwards, most would know it wouldnt be from just over idle at that point...apologies for any confusion there to anyone. I took the o.p's "typical" to mean of the spec he was tuning...i.e a ported head, fast road cam etc...which "should" make "around" 140hp with a decent ported head/corect cam timing. I was under the impression that DC75's engine was standard in the head & cam department?..so not really the same or similar even on the same rolling road..again, appologies if DC75 has indeed a cam & ported head, which would obviously then render it similar. From the engines I've tested in "fast road" form...ported head, 270/280 cam, 10-11:1 c.r, they all appear to like around 28 degree's full advance at peak power at around 5,500-6000rpm, and dont have a pinking issue at peak torque at around 3500rpm. Much over 28 degree's and the power doesnt climb and/or a trace of pinking starts to come into play. My race engines on 13:1 c.r & tight squish bands wont take much over 24 degree's between peak, full load torque & peak full load power, some a little less, but at over 105hp per litre I can live with that. Dispite popular opinion, just because a car is tested on a Dyno Dynamics rolling road it doesnt automatically make it god like I'm affraid...I have it on good authority that they can fluctuate...like any other dyno or piece of test equipment...and have been known to give very different readings with the same car on the same day with no changes to the car...odd but true. Again, for the record, I have "no reason" to believe that to be the case with the dyno examples quoted in this post using the equipment/locations stated, as the figures we see from the tests done in the past appear to be in the right ballpark...however, power @ the wheels would be nice/interesting to see though as that is where the measurement is taken so should be in the system somewhere for comparrison. Good luck with the project beyondhelp...shout if you want a starting point for the cam timing if you go that far for your customer.
Breathing Hi, this car is a joint venture by myself and a mate that we decided to do after one track day in his RS4 cost him 5k of repairs. I will be fitting a TSR 4 branch and having a play with the cam timing over the next coupe of weeks. I feel there is a breathing restriction at work at the higher end of the rev range so I will be looking to address this asap. The cam is a 270 degree Kent one with uprated valve springs. The valves were milled down to get rid of the "thicker" end of the stem but I may well get bigger valves.. any advice here would be much appreciated as thats unknown territory for me. Im currently outing the geabox as it ate a syncromesh on track this week so once this is done I will update the difference with the 4 branch and cam timing. I would like to know what your views are on the latter of these please.
Hello buddy Ah cool, good call....ouch...that musta hurt! In fairness to the std exhaust manifold & downpipe, they work well with fast road type cams like you currently have, so the gains from a manifold will be small as the current set up wont be causing a bottle neck...but a manifold will give a small gain and pave the way for the future if you upgrade. The TSR long primary manifolds work well. Cam timing is very important...I've seen anything from 10 to over 30hp gains by correcting cam timing. Forget cam timing figures, advance/retard on the pulley (do you have a vernier pulley fitted?)...you need to find the true TDC direct off a piston through the plug hole...ignore the crank pulley & flywheel timing marks. Once that is done, in simple terms the inlet lift @ tdc needs to be 10-15 thou more than the exhaust lift...so if the inlet lift is say 100 thou @ tdc the exhaust needs to be 85-90..adjust the cam timing until you achieve that ballance, that will give you advanced timing which is what you want. No doubt yr man who did the Omex install will be able to do it, or pm me for full details...though there are guides on here if you want to search them out. Thinning or "undercutting" valve stems at the lower point needs to be treated with extreame caution!...single piece valves can be thinned in moderation, two piece valves can be weakened...loosing a valve head wont be much fun at the expence of extra flow. Bigger valves are always worthwhile but it's a law of diminishing returns...a good ported head on std valves will flow enough air to make 170 with ease with a more radical cam & open induction, so will work fine on your spec. The first step up in inlet valve size is 40.5mm...0.5mm bigger than std. This will fit on the std seat insert with the seats re-cut to suit, and a gain of around 3-4hp can be found...approx 1/3 more than the ported head should have given in the first place...not huge but a set of valves and seat re-cutting, plus light re-porting to suit...it's totally pointless just dropping them into re-cut seats. After that you'll need bigger seat inserts & a fair bit more machining work, but 42mm inlets & 35mm exhausts can then be fitted in place of the std 40/33's. Most at this stage will shout "fit a 16v"!...and I must admit it is a more cost effective option and would work well with yr Omex set up...it's all down to what flicks yr switch and if you want to be swapping engines or head work...depends how good yr current engine is v's an engine of unknown quantity and what you ultimatly want to achive. If you stick with the 8v route then consider more cam options in the 280-285 degree region. You'll need more c.r at this point via either skimming the head or the preferable option of decking the block to reduce piston volume and taking less off the head...and/or poss consider a 2ltr block at this point...depends on the current pistons used...didnt yr Omex man mention uprated pistons had been fitted? If the box is coming out, consider a final drive ratio drop and a Quaife ATB diff...subject to budget....it's very easy to get carried away! Either way...welcome to the tuning bug!
Thanks Mr Hillclimber, evolution of the car follows this trend... build a good 8v motor and learn to drive on track with moderate power. As our kill increases, add the power to the limit of the 8v capability. We may well not go the 16v route and go straight to std power 20vt power plant. In essence, we dont want to have more power than we are capable of handling as we are quite new to track day driving. I dont think from what you are saying that we will need to mess with the valves.. our losses would seem to come from cam timing so this is what I will tackle first. Then take a look at the cam itself.. I thought anything over a 270 would be too much as it goes on the road too but not very often. The engine is a PB unit taken out to max bore with racing pistons and rings. Crank was reground, balanced and fitted using plastigage 010 Mains and 020 Big End distances. Conrods and pistons were lightened and balanced, head skimmed but I need to check the CR.. will be higher than stock. Flywheel was lightened and balanced also. Head was ported and polished by a guy I know well who builds racing engines.. mainly ford and he gets good results from them. The downpipe will help with breathing a bit and will sound great with the powerflow system Gearbox is just having new syncros and the diff rivets changed to bolts.. trying to find a kit for this. All said, could we see the gains we need with cam timing sorted and this spec? Looking for 160 bhp and a nice bit of torque for us as track day muppets By the way, we have koni suspension with braces at the front and rear, fully poly bushed, 6 point roll cage, racing seats and 4 point harnesses. Was a blast building it, not done anything on this scale before.
As our kill increases, should read Skill Dont have an edit button for some reason I like your website by the way, very nice black Mk1 gti you have there
Thanks alot...there's a new site coming soon with a few tweeks. The o'll crate is'nt bad...it's served me very well over the years. Yeah I guessed thats what you ment... Moderate power could indeed come from a multi valve engine still without being OTT, but as you already have a sound base by the looks of it there's nothing wrong at all sticking with it to achieve your aim. As for the limit of the 8v...well 200+hp is on the cards but you would need some trick bits to get there, though a realistic 160hp can be had with the right parts on a plenum, and your stand alone control for the fuel & ignition management is a great starting point. A 270 cam is very mild, though in your case power spread is good so the timing may not be a million miles off, though as it only costs time to check you've nothing to loose. You wont however see 160hp...at least not a genuine 160..on a 270 cam...though I'd be inclined to say dont look at numbers at this stage..get out on track once you have the best with what you currently have and get some seat time under your belt. Staying on a plenum, consider a 285 degree cam as a good compromise...a friend of mine runs a 284 degree cam on the road on old tech k-jet in a 2ltr and thats perfectly ok...no lack of low end grunt or drivability issues there. More cam could be used but yr starting to get toward needing better components to make them work, along with ever increasing c.r's & rpm. What pistons do you have...cast or forged? not all interpritations of racing pistons are the same. VW used to do a diff bolt repair kit, though you should be able to find one on-line. Suspension & brakes are much more important than hp in the early stage of learning both a car and track, along with decent tyres. Once you cant get it to go any faster round a corner then look for more power.
Cheers mate! Yes I meant the "old crate" but its hardly that! I have and always will have a soft spot for the old mk1 gti, I had one when I was 18 which was about a million years ago.. and a convertible.. both black. I will take your advice. the car handles great, really predictable. Little bit of understeer, no oversteer found yet. messing with the tyre pressures made a huge difference and we saw some air under one of the rear wheels a few times. didnt even realise this until we saw the easy tracks photos! We found ourselves very quick through the corners being held up by elise's and clios but we just didnt have the needed power to get past them on the straights. This was before the Omex install so with a few tweeks we may find we have enough to keep us safe on track until our driving skills Improve I will find out about the pistons as I have no idea if they were forged or cast. Happy days
Cool...let us know how you get on...from the extra urge yr tuner found you should certainly feel the difference. Once you've got used to that there's plenty more possible.
Well, cam timing is miles out! For the record, that was my error, not the people that fitted the Omex as they didnt go near that. I have a vernier pully on order so I can sort it properly! Im looking into different cam options up to 285, want to make sure I dont have any issues with valves hitting pistons (alot of this is pretty new to me). First job to do is the gearbox synchros and the diff bolts.. that should be done in a few weeks.. why is the ratio between work and what you would rather be doing never in your favour !
Did you check lift @ tdc? You wont get a piston to valve problem unless the head has been skimmed to death and the pistons protrude a good bit. You'll ideally need to know the current c.r as just fitting a wilder cam may not be suitable to what you have. If the cam is a long way out you'll notice the performance difference..the downside is the mapping will need looking at again as the requirements will change.
Yes, I followed what you said and found true TDC. Not a problem about the remap, its nicely located next to the dyno place so we will just have to do that again too I will let you know how it goes. Thanks for all the advice Mr Hillclimber, yer a gent!
update Hi again, here for an update. Its been a while as I broke my leg in a more than foolish way on an airsoft weekend but back in business now. So, from last post I have rebuilt the 020 gearbox, new syncros, seals, bearings and arp diff bolt kit. TSR 4 branch is now on and the cam timing setup properly. After doing the timing, we discovered one of the rear wheel bearings was totally knackered so we parked the car overnight and upon our return to continue, it would not start! No fuel or spark [:^(]. Immobiliser disengages fine, you hear the fuel pump prime but it just turns over. Bearing in mind we run an Omex 600 setup I am suspecting the crank sensor but I dont know what Ohms values to expect to see. I removed it and checked with a meter and its reading zero ohms.. doesnt seem right to me but I cant find any values for it, its a 2 pin magnetic VR type, can anyone tell me what resistance and voltage values should read? The car started fine from cold after the cam timing was reset, idled fine. Didnt drive it however because of the rear bearing. no wires were damaged or sensors knocked and I have checked the loom for cuts/breaks. Battery is fine and the ECU is seeing voltage at the cranking stage of ignition. What do you guys think???
Right, got the laptop on the Omex today and saw the static sync value staying "OFF" when cranking. Tried waving a screwdriver past the sensor and still nothing so its new sensor time tomorrow and see if she fires.. hate it when the shops are closed!!!
