GT74 High Compression Six Speed

 

I am not sure of costs involved, have you any info Dan?

I looked into this a long time ago Phil as I was working on cast iron heads and wanted to do all I could to maximise ignition timing, ward off det and keep as much load out of the cooling system as possible. I ended up not being 100% confident in ceramic coating in the chamber itself or the piston top (although other people were doing it) and I could only justify exhaust port coating (to help the coolant system). It wasn't that expensive and something like £45 per port springs to mind.

I pretty sure I was speaking to Poeton in Gloucester at the time as they are local to me but this was over 10 years ago. I think the Apticote 420D is/was used for heat reflective purposes in the chamber. Apticote 200 or 200M is/was used on skirts for friction purposes.

I hope that is of some use to you....I do have some printed info tucked away somewhere and if I can find it I'll scan it and post it up.

Thanks or your input Chris, much appreciated. When you say high compression, what sort of static ratio are we talking about? The HKS 280 cams I am running do have a long duration and over lap which does cause breathing issues at low rpm, which makes idle interesting, as it just does not want to suck. However lift is still only 9.3mm where as Brian Crower cams lift to 10.79mm, but I am not sure of their duration. Do you know of other cams that meet the high lift a criteria? If I am to open up ther motor I would like to push the compression and fit with the best cams I can afford.

I think the WRC cars were running about 9.8 to 1, with specialised cams, and direct port water injection using a Bosch water pump and Bosch port injectors spraying onto the backs of the inlet valves. I may be able to find out more, but be aware these things were built using manufacturers budgets and their engine dyno facilities. I wouldn't attempt one myself, but that is not to say you can't attempt such a build. You need to speak to people involved with late WRC engines really.

280 degree cams are still fairly tame, the only reason they shouldn't idle around 1000 RPM perfectly reliably is if you are still running an AFM system. I assume you are on a throttle angle / MAP / RPM system?

taking on more compression in your setup will not increase the motors ability.. we are already sacrificing timing at high rpm so ward off knock. even with a low dynamic compression( the 280s) and at the moment on the current tune (1 bar boost) this is not causing any significant egt rise. but i think that at 1.4-1.6bar (i.e where the higher power figures will be obtained )the timing will surely be causing high/unacceptable egts which means dropping boost off to be able to run greater ign angle and lower egts.

the only reason racers are using 12:1 in a boosted motor is because of the fuel which they are running on is capable of sustaining knock free running at those cylinder pressures.

ideally your motor is designed to be running on an high octane blend. rather than pump super. hence the sacrifice in timing which is going to be a lot more noticeable at higher boost.

then again.. these last few posts are only due to the cock/muppet/dickhead that sold you that motor!!! borewash on run in anyone??

then again.. these last few posts are only due to the cock/muppet/$#@! that sold you that motor!!! borewash on run in anyone??

Oh dear

 

then again.. these last few posts are only due to the cock/muppet/dickhead that sold you that motor!!! borewash on run in anyone??

I take it there is a problem with the engine? reading between the lines here but how can the problem be down to the run in period as from reading Phills posts its been running perfect for ages?

Shit happens:innocent:, it has been running fine, we just can't take the boost higher or push the timing as the ring/bore seal is not good enough. I think when we first started it, we hoped that the initial blow by was down to rings being stuck, due to the motor being sat for a while and needing to be freed up. After a week however, we realised that a rebuild was inevitable, if we were to get a near perfect bore seal, which we would need if we were to take the car to its upper boost limit. Incidentally the blow by has remained pretty much constant, decreasing slightly as the motor gets to temperature. I don't go above 4000 rpm until the oil is at 90+. The plugs always look fine after it has been given a thrashing.

Thats life in the world of highly modified engines. Having made the decision months ago that the engine had to come out, we decided just to see how the motor would perform as for the UK we think it was unique at the time. I really like the way the high compression motor brings on early performance on such a large turbo. This problem has not put me off one bit, it has made me determined to get this motor working to perfection, as its potential is just out of reach.

After reading Chris's post about 9.8:1 being high compression in a forced induction motor, I will stick to 9.5:1, I may look into ceramic coating the chamber, crank, rods ring pistons and cams to reduce oil drag, but only if it looks cost effective in terms of the over all cost of this project. I may possibly play with a more wild cam set up. If I can get close to 1000 at the wheels I will be exceptionally happy, but I would settle for 1010 - 1020 at the crank.

I am very patient, so am in no rush to get the motor out just yet, I can wait to get the car how I want it. I have spare blocks cranks and a head so I can get much of the work done before the motor has to come out. We also will have the advantage of a good map from the first turn of the key, and this time we will be in control of the run in procedure. We will have another head gasket in the collection we have, that marks the rebuild of every engine we have had to strip. What is really exciting is the car is fantastically fast, even with the ring issue, so when that is fixed it will be even more insane.

Good luck with the rebuild, is the gt74 big enough for 1000rwhp or are you changing to a larger turbo?

Good luck with the rebuild, is the gt74 big enough for 1000rwhp or are you changing to a larger turbo?

You would expect to get 750rwhp tops out of the GT74 on a standard compression engine. Ryan Woon got 873RW(USA) on a standard compression engine. So what the turbo is capable of on my engine build is unknown. I will need a different turbo to see four digits in front of RWHP. It is the journey getting there that is half the fun. All the above assumes race fuel.

Good luck Phil, please keep this thread updated with the progress

Opps

Just spent the day on the track in our RB powered 200SX. I thought I was writing an email to a friend but posted it here by mistake. Totally knackered, so off to bed.

You would expect to get 750rwhp tops out of the GT74 on a standard compression engine. Ryan Woon got 873RW(USA) on a standard compression engine. So what the turbo is capable of on my engine build is unknown. I will need a different turbo to see four digits in front of RWHP. It is the journey getting there that is half the fun. All the above assumes race fuel.

I wouldn't put too much faith on US dyno number. I mean, several of them are pushing the stock twins to 450 - 500 rwhp.

Brad D pushed his GT74 to 811rwhp at 31psi - stock short block and 264 cams.

I wouldn't put too much faith on US dyno number. I mean, several of them are pushing the stock twins to 450 - 500 rwhp.

 

Brad D pushed his GT74 to 811rwhp at 31psi - stock short block and 264 cams.

I don't have faith in US dyno numbers, their horse have short legs so they need more of them;)

As yet I don't have anything else to compare my car with over here. My engine spec is very different from Ryan Woon's engine which he used to test the stock GT74 DBB. High compression, 1mm oversize valves, 280 cams and 9000 rpm limit and my turbo is modified . One day I might stick the car on on race fuel and take it for a trip to Bruntingthore to see what it is really capable of achieving.

No offence to anyone intended, but dyno numbers are not important to me. I will put the car on a dyno to finish off the mapping as it would be unsafe to do it on tarmac. I am only interested in distance/time.

I don't have faith in US dyno numbers, their horse have short legs so they need more of them;)

 

As yet I don't have anything else to compare my car with over here. My engine spec is very different from Ryan Woon's engine which he used to test the stock GT74 DBB. High compression, 1mm oversize valves, 280 cams and 9000 rpm limit and my turbo is modified . One day I might stick the car on on race fuel and take it for a trip to Bruntingthore to see what it is really capable of achieving.

 

No offence to anyone intended, but dyno numbers are not important to me. I will put the car on a dyno to finish off the mapping as it would be unsafe to do it on tarmac. I am only interested in distance/time.

That sounds very wise.

I am mostly curious how that GT74 spools, that is why I would like to see a dyno sheet.

the motor runs good. makes very good power and doesnt do anything apart from use more oil than expected. hence the swearing at whoever ran it in.. or built it.. im assured the builder was top notch. but the engine was used before phil got it. seems a very common misconception to run in engines richer than usual from the amount of people that have asked about the subject.. since when were car engines 2stroke? unless your a trabant/saab man! lol then again.. look at most of the after market ecus which come with a base map.. fuelling is usually very poorly metered in the "i'll just drive it gently to my tuners" which is 400 miles away.. 3 tanks of fuel and set of plugs later you arrive for a very smoky mapping session..!!! im glad wideband o2 has become common and people understand what they mean nowadays.

Nothing has happened to the car since since February. It is just being driven once or twice a week so I can get use to it, especially with no traction control. Hopeful we will put the test 1000cc injectors in this week and adjust the map to suit, and squeeze a bit more power from the motor.

imho i doesnt need TC!!!! your being a girl Phillipa...

If you recall I said that I had not really felt the need for it, since putting the car back on the road, even with the power levels I have. As RLTC was already half wired to the car, I thought I would keep it. It is a good system and I did not want to sell it. I have refitted it, tested it and know it works and will be keeping it for when it is wet and the roads are cold and traction levels are poor. When 295 rear tyres will not be the best ones to have. If I had not experienced RLTC before , I probably would not have fitted it now. The six speed box makes a world of difference, as you are not insulated from the the feel of rear wheels as much as you are in an auto.

I think I have sorted the expansion tank issues, related to the small replacement for the stock tank. As for the previous oil issues, it does puff on start up, as we suspected a couple of VSO's have gone. I have two spare sets so just need to change them. Apart from that it is fine. More than fine, it is amazing. The map copes really well with the heat, oil, water and EG temps are fairly low, and AFR's are spot on, the grip levels at the rear are incredible. I have driven it every night this week and enjoyed every minute. The miles are clocking up and everything is working very well. I am not sure how long the auto diff will last as, 8750 rpm is so addictive, the experience is fantastic. The only down side is the rev limiter gets in the way;) I must stop bouncing off it.

To use Dude's sig, it is; Sit down, Shut up, Hold on.:flame:

8750rpms, bet that sounds awesome

Are you going to bring the car to Suprapod Phil?

Hi Phil, what sort of MPG can you achieve on a steady run with this high compression setup?

Thanks, Jason.

Hmmm I'll have to try a steady run, not don't one yet as it just begs to go fast so about 10mpg at the moment:d Earlier in the year I did try once, to do a light footed journey and got around, 26 mpg between fills but the journey was only 70 miles between petrol stations on the A1 so apart from pulling back on to the road and stopping again it was a steady 70. Not really enough miles to judge. If I drove it like my granny and stayed of boost it might get 28 -30 at a push. I really have tried to see what it can do for economy, but it just gets so boring and then I want to hear the engine scream again and oops 5mpg again.

Now the exhaust system has got deposits built up inside it does not sound quite so harsh as it did when we first used the system.

No plans for Pod, far to busy.

I plan to do some more dBA noise tests as my original dB meter was under reading at sound levels above 100dbA, I have a professional one now with a calibrator, so levels should be accurate. To me it it sounds amazing, from 4000 to 8750. It sounds nothing like the car when it was just BPU. The 280 cams really come alive from 6000 rpm, when it is mental. The only sound clips I have were taken on crappy cameras so don't really do it justice. So I must record some better ones with a quality stereo mic.

8750!!! That must sound amazing. Your tach must be bending the needle as mine shows 8K when in fact its powerFC limited to 7600. Can't wait for the vids!

8750!!! That must sound amazing. Your tach must be bending the needle as mine shows 8K when in fact its power FC limited to 7600. Can't wait for the vids!

I have a TRD 10000 rpm taco, it is pretty accurate as it shows my AEM set limit. Bouncing off the higher limiter was a new experience though.

The camera was being held by a passenger in the clip below.

I am trying to find a reasonable camera mount as my good one is welded into our Skyline RB25/200SX. Then I'll take some clips.

I got a number of enquiries about my Jun style plenum at Pod at the week end.

These shots show the plenum before it was port matched and fitted to the car.

 

The camera was being held by a passenger in the clip below.

 

http://i133.photobucket.com/albums/q55/Devilstorque/th_075bar_0001.jpg

 

I am trying to find a reasonable camera mount as my good one is welded into our Skyline RB25/200SX. Then I'll take some clips.

That is awsome dude

The speedo was giving a 7% error, but it still was impressive, reaching well over 170 on the runway. Since fitting a speedo adjuster, the clock is accurate now from 30 all the way in to big triple figures, all matching SAT NAV GPS figures.