924Board.org

[PORSCHEV]

I had a very good year for my first season of paved oval track racing. I made 16 wins out of 22 starts and always finished at least top 3 out of 9 cars. 3 race days ago I moved up into the modified 4 cylinder class where I can beat 2 of the cars with out too much effort. (toyota celica and honda crx) The cars I can't touch are the dodge neon's and one other crx.

First off the engine is supposed to be stock..but somehow the rules have been stretched and the neons have been allowed to drop in an engine from a dodge stratus that are 150 hp stock. I have 110hp.

The modified part in the class is the suspension and tires. I have 2 sets of goodyear eagle racing slicks that are 8.5 inches wide that will get me through the corners fast. I ran 3 race days on a set of worn out toyo proxies and did pretty good and would have done excellent with more right front chamber. I was maxed on the stock settings.

On to my engine build. I need to make at least 140 hp. Plans are to up the compression.
Is it feasible to just plain the block by 2 mm to get a higher compression or should I get a set of euro pistons?

What year head breaths the best in an N/A head? I currently have the 79 non euro.
I also would like to look into putting in larger valves and porting, but I understand some say it's a waste of time in an NA head.
I will be installing an audi TB valve as well as a stage 1 or stage 2 cam. As well as getting the flywheel lightened.

The car is currently wieghed in at 1983lbs and I would like to get it down to at least 1900 before next year.

In a perfect world the rules should have let me compete bone stock..but the track owner has let these neon's run with these monster motors and I have been given the green light to build my engine to compete. So no preaching about cheating The tech guy doesn't get in deep enough to detect the cam profiles or tell if your ported or how big a valve your running etc. More likely to check your cubic inches to see if your running a stroker or bored out big. BTW I don't want to build an interference engine.

Right now the fastest lap time I can turn is around 20.5 for the 3/8 mile.
The neon's can run 19.1 So in a 20 lap feature they have lapped me.


Thanks in advance for the help guys.

[bass gt]

If you want to optimise your power, you need to throw away the CIS and install ITB's and a new ECU. Decent timing and fuelling will give you the best returns, and will maximise any benefits cams, head work ect give you. Obviously, if this is allowed in the series.
Simon (Simsport) managed about 140 from his weber carbed NA before going supercharged.

Regards,

Steve
_________________
Front Wheel Drive is the Devil's work.

[Raceboy]

You could use 931 head, VW flat top pistons and deck the block up to 2mm. That is THE MAXIMUM amount without having to look for shorter timing belt. BTDT. That would yield decent CR for that engine and it would be cheaper than to upgrade stock NA head to bigger valves, porting etc. Not to mention the result would be better.

We used stock Euro pistons and decked the block 2mm's w/ 931 head. CR was around 10.5, but with VW flat tops you will get higher CR (=better). That resulted 120rwhp on the Dynocom dyno. Of course, we used engine management, but with K-Jet you shouldn't lose more than 5-10 whp I presume.
_________________
'83 924 2.6 16v Turbo, 470hp
'67 911 2.4S hotrod
'90 944 S2 Cabriolet
'78 924 Carrera GT replica
'84 928 S, sold
'91 944 S2, sold
'82 924S/931 "Gulf", sold
'84 924, turbocharged, sold.
http://www.facebook.com/vemsporsche

[924RACR]

I'm with Raceboy on this one - that should get you where you need to be handily. I'm making an estimated 125-130 crank hp with stock cam, stock 924 head with mild port-matching, MSDS header, 9.5:1 CR and .040 overbore. Indeed, I suspect that with good bottom-end work (balancing, mild lightening, and the flywheel lightening, open up the clearances, crank scraper, etc), a good cam, and good top end work, race valve job, you may get the 140 you're looking for, perhaps even without having to buy new pistons or head.

After all, if you can keep the engine cost down, you can do some nice shocks, and that would probably help a lot too... unless your track is as smooth as a billiard table!
_________________
Vaughan Scott
Webmeister
'79 924 #77 SCCA H Prod racecar
'82 931 Plat. Silver
#25 Hidari Firefly P2 sports prototype

[PORSCHEV]

I have thought about the VW flat tops and did some searches on the board but haven't been able to find out exactly what set to buy. I also am not clear on what the compression ratio would be and what all has to be done to get the wrist pins to work for me.

If I go with the 931 head..can I use my stock intake and exhaust manifold? The header would be a dead give away considering it is not at all allowed in the rules. Another question would be if i go with the 931 head what cam do I use...does the 924 cam and followers fit.

Bass gt...I would love to upgrade the fuel system..but that is way outside the rules.

924racer...The track is actually very smooth....only 1 small bump in the exit of turn 2 of the center lane. I am running a set of heavy mustang coil spring up front. I do need to get some camber plates for the struts.


I also have plans to get some adjustable sway bar links to preload the left side down as I tend to lift that wheel right off the ground when I corner going into turn 1.

Sorry getting off topic...

I like your idea raceboy..I am going to look into it further so any info you can provide post it here I would appretciate it.
_________________
1976 924
5 lug conversion, 17'C2 wheels,custom body work,327 vette engine.

1978-#53 "D" track racer.

[Raceboy]

You just need to buy new rod bushings from ebsracing or have them custom made.

You need VW flat-tops that have 39.6mm compression height.

You can modify stock inlet manifold but it's better to use 931 one, it looks very stock also.

As for exaust, it's not so simple as bolt spacing is a bit off and ports are larger but it's worth it (grinding it).

Stock 924 cam and followers work fine on 931, they are the same
_________________
'83 924 2.6 16v Turbo, 470hp
'67 911 2.4S hotrod
'90 944 S2 Cabriolet
'78 924 Carrera GT replica
'84 928 S, sold
'91 944 S2, sold
'82 924S/931 "Gulf", sold
'84 924, turbocharged, sold.
http://www.facebook.com/vemsporsche

[Racing]

For the sake of argument.
Any otto engine will have its efficieny increase in a more or less linear mode as compression goes up until approx 13.5:1.
Now..it is also imperative to view that from the perspective of dynamic comp more than anything else in such case.
No matter,it is imperative to run comp on the edge as this IS allowed and this IS a restrictor class.

VE needs to be brought up at all ends to the best of knowledge/possibility.

Ie;if it is allowed to play around with the intake,toss the OEM one and build one up scratch to meet your goals.
ANYTHING that will produce a pressure drop is BAD,and as such i at leat advice on doing it the "right" way.
From this respect ANY OEM intake sux.
TB..use whatever fills your engines demands.

Cams then...are dictated by head flow and intended rev/power range seeked out.
This is where the 24/31 engine comes up short,cause in essence it simply sux.
Main culprit of both head is that the intakes as well as exhaust ports were not designed to support a high power engine.
On the other hand,if you´re allowed to fool around with the cylinder head-what´s keeping you from more or less redesigning it?
Ie,for the intake,hog the SOB out and bring out the TIG welder.

As an example;



Someone got seriously fed up witht he inherent restrictions of a BMW M10 cyl head,and ended up porting it out..installing oversize valves...and in the end welded the 54mm runners directly to the head.

Admitted..this for EFI...but none the less.

[924RACR]

The adjustable rear end-links sound like a GREAT idea!! They're also CHEAP - just buy pairs of metric rod-ends, 2 male, 2 female, and screw them together. IIRC Chassis Shop sells them (http://www.chassisshop.com/) if you don't have a local retailer. You might need one spacer on the trailing arm bolt, but a stack of washers could do the job.
_________________
Vaughan Scott
Webmeister
'79 924 #77 SCCA H Prod racecar
'82 931 Plat. Silver
#25 Hidari Firefly P2 sports prototype

[simsport]

If you are stuck with standard fuel and ignition I suggest you get the distirbutor recurved to help you run the car on the track. Also fit an uprated spring in the WUR as I think the CIS is a bit lean at higher revs.

Blueprint the cam/valve heights etc as its about all you can do to add anything to the stock head without porting it and a change of cam and exhaust manifild.

Its a safe engine as stock so, if you can withn the rules, fit the light piper followers and spring caps....it will allow a few more revs.

With a std head the car will det on normal fuel if you take off more than about 40thou from the block....or at least mine did!

Fit a crank scraper...might be worth about 4bhp. Also us the thinnest oil you can without loss of oil pressure....oil pumping is work....work is power!

Do you have to use std alternator and water pump?
If not ditch them and run a small alternator unit and if possible deactivate it when in an actual event. Fit an electric pump...will give you power.

Feed cold air to the airbox but do not cut the face of it off as it disrupts the airflow to the plate in the airflow meter unit.

Work on the aero side of things...close of gaps at the front and if wipers are fitted run them vertical and not across the car.
Fit a flush screen if you can...it all helps!

Cheers
Simon
_________________
Blown is always best!

[PORSCHEV]

Thanks for the advice simsport. I was planning the crank scrapper as well and lightening the flywheel by 6-7 lbs. Along with now running either 9.3:1 pistons or the vw flat tops. Along with a 931 head with maybe even some port work and maybe even larger vlaves installed.

If I can get 140hp I would be more then happy. Does any one has the torque out put that this typ of build would put out.
_________________
1976 924
5 lug conversion, 17'C2 wheels,custom body work,327 vette engine.

1978-#53 "D" track racer.

[924RACR]

My torque curve is VERY flat, very stout from 3000-5000. Sorry, nothing scanned, but if you email me real nice maybe I'll send an excel file of a few pulls.

Simon - good point about timing... run 43 degrees total max advance, just pin the distributor, no vacuum or mechanical advance. Canceling out the vacuum is easy; if you disassemble the thing we've just recently found that you can rotate the upper half 90 degrees and there's a perfect little hole for the pin from the vacuum unit to fit in and stay put... rigging the mechanical is a little trickier, but do-able... heck, even if you have it, that's not a horrible thing, just lubricate everything properly so it's consistent.
_________________
Vaughan Scott
Webmeister
'79 924 #77 SCCA H Prod racecar
'82 931 Plat. Silver
#25 Hidari Firefly P2 sports prototype