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I thought since being a long time lurker and finally getting a moment to put things together for a build thread, I should do so!
So far over the past couple year's we have been running this car in PTD/TTD and ST5/TT5 with decent success but have decided recently to step up another class into ST4/TT4 for 2019.
Last years 5 class trim with 1.6L of fury....
A little clip from the end of the 2018 season chasing a american iron mustang at heartland park....
We did do decent at nationals last year at COTA with a 3rd place in TT and qualifying 3rd in ST with our little 1.6 but had the timing belt jump a few teeth exiting the first turn for the championship race :(
We had a lot of fun with it in that state but it's time to go a little faster now so here we go with a few specs...
Engine is 2006 LE5 ecotec and AR5 trans staying internally stock for at least dyno runs and testing to get a baseline before building it since we only have guess's at the moment as to what power it will produce. Engine will be operated with the factory ECU. On to the pics!
So that's where we currently are! Should be making noise soon after I get done wiring it up over the next weekend or so and then on to wheel flares and some aero changes!
Last edited by gt5759; 08-03-2019 at 03:24 PM.
Reason: Cats
After getting two other race cars done for other people I was finaly able to get back onto ours with not much time left before our season starts.
Wheel flares are done and installed. New light weight top is fitted and nutsert's installed for polycarbonate window attachment, top is currently being painted.
Wiring is complete and tested with base tune finished, just need to remove the harness for looming and final installation then off to the dyno to dial it in and see where we land. I still need to weigh, balance and align the car but it should all come together pretty quick. Here's a few shots from this past weekend!
Still need to update/change vinyl's on the car as well.
Finally got some time to start finishing things up! Engine bay for the most part is complete other than a couple heat shields I'm going to make for the header and intake, a little something to separate radiant heat from wiring and air filter. The cerakote does well to reduce temps but I'd rather insure no problems down the road.
Tuning wise I had to stop as I am out of injector, kinda figured this would happen as stock injectors are only 24lb. I got some 640's from Nigel@flow force on the way for next week that should get us where we need to be.
Problem number two is the driveshaft I had built has play in the slip joint, so back to the builder for the fix, I will hopefully have that back by next week as well.
Few shots of things buttoning up for now!
Finally installed my helmet blower while finishing the new ecu install as well.
Well after a lot of trial and error we finally got the car on the track but not without a fight and still not 100% complete.
Some pics of the build so far and sorry if I bounce around a little in the order of things.
Corner weights came out good, all in all we gained 100lbs from converting to ST4 - that includes brake upgrades all around plus larger wheels and tires.
Numbers are with 3/4 tank of fuel.
Oil pan had its issues with pick up problems under G's so we had to redesign the baffling with some trap doors this time, works perfect now with no noted pressure loss on the datalogs.
Biggest issue we came across was a crank signal error due to some sort of harmonics in the engine, I'm gathering it was from the balance shaft delete as my research never came across anyone having this issue before with this engine. After some trial and error we got the haltech ecu to get past the problem with some edge rejection and filtering.
Once we got around that we found the drive shaft design we have is horrible and vibrates badly, so no going above 5000 rpm in 4th gear without fear of breaking something. We spent several hours trying different pinion angles and driveshaft clocking with no improvements at the track. So building a new shaft is next to fix the issue.
Other than that the chassis feels great, brakes work perfect and the power output is awesome. So still feeling good about it all even with the challenges thus far.
Well the new drive shaft is in and spins smoothly on the lift in 5th gear to 7400rpm so we're loading it up to take it back to the dyno for some final numbers and a upcoming race next week!
New design I had built consisted of cutting the front section of a factory solstice driveshaft, 2" tubing and using the common miata rear flange replacement, also installed a new cv joint after having the new shaft built.
After sorting through the little problems that come with engineering something it does exactly what I had hoped for power wise, perfect for the class and pretty impressive for a stock 40k mile motor with just my intake manifold and exhaust design! Next weeks race is going to be great i think!!
Well after a long hot and humid weekend the car is working great and is proving to be towards the pointy end of ST4. Lots of little things that need addressed to make the car faster and fix little annoying things but overall I'd say were 90%.
Set both track records on Saturday in 100* weather with high humidity, it was not good for fast times so we were very surprised. This fall we will be a rocket with better conditions, my estimation is about 2 seconds faster. Sunday was a bummer as the 12v supply wire broke inside the connector just before the crimp on the #1 coil and we didnt have the parts to fix it.
We had a decent field of 7 this weekend so that was nice, we were missing two others that normally show up, which would have been cool to have 9. It appears st4 is shaping up here in the midwest - turbo nc, couple bmws, porsche boxsters, 350z, rx8, s2000's..... wide variety.
The list of changes! Gearing is horrible with the current 3.90's, 4.30 should be closer to what it wants, 4.77 I think will be too short looking at the numbers. Hubs need replaced and upgraded, probably going to go with the wilwood option.
Still have a slight driveline vibration so I'm going to go back through all the angles and have the balance on the shaft checked again, the new cv I installed on the end of the shaft might have changed the balance.
Some alignment changes to make as well as some spring rate changes, nothing dramatic as the I'm pretty happy with that department but some fine tuning will make some gains.
Fun fact, the mustang's late in the video are pro drivers in IMSA GT4, PF Racing, apparently using our track weekend for testing purposes, they are bad ***! I have another vid I need to process from the second race that I start gaining on a white one, very slowly but still gaining, probably something wrong with the car but still makes you feel good haha.
Also here mainly to just say holy ******* **** what a pathetic driver in that unlimited Corvette. That would have sucked if he collected you when he decided to stick it in and ended up spinning.
Also here mainly to just say holy ******* **** what a pathetic driver in that unlimited Corvette. That would have sucked if he collected you when he decided to stick it in and ended up spinning.
Yeah I was waiting for the hit. That guy is scared of that car and he's been racing it for a while now, wish I could take it out as I bet it's an animal.
We'll unfortunately I can't go to nationals this year but will be in spirit as I prep cars to go. Some of you might remember this one...
Needed much love as it's changed hands a few times and been through a few shops since its conception.
Hopefully I can get to ours this weekend for some work but were still putting the new shop together so things are a mess right now.
The guy in that Vette is terrifying to say the least. Charges in, then brakes early like he is going to concede the corner, then back off the brakes and............geez.
Good drive, but where are the other ST4 cars, well behind you? You should detune/ballast come to a GLTC race, 35+ car fields are fun.
Also, that vette driver suckkkssss. OSB for sure
Yeah the other ST4 cars were a ways off the pace.
I've been thinking about trying GLTC as I have some friend's running in it but scheduling wise it's just not in the cards at the moment. Might do it next year but will need to plan ahead not only for vacation time but necessary changes to the car to meet the rules.
The season ended up pretty good overall! We won all 4 races over the weekend, set both track records again for TT/ ST, ended up TT season champion and would have had the ST championship but didn't have enough events to qualify for the year due to the teething issues with the car. Next season will be better.
Stock hubs hate life on this thing so upgrading is due. We installed the new Wilwood hubs on the LS swapped miata this event with great results so were going to install those on this one as well. Only issue we had with the Wilwood hubs is they use bolts instead of studs and the bolts they supply are only about 50mm in length from the face of the hub to the tip of the bolt. I drilled the bolt holes out and pressed in the ARP studs that we had in the stock hubs. I'm not entirely sure as to why Wilwood made that design decision by using bolts but easy enough to fix. Rear hubs I'm leaning towards the V8 roadsters upgraded replacments.
Swapping out all the bushings to either SADFAB's package or spherical's (if the budget allows) is going to be on the list as well along with building a spline/keyed torsion bar setup and ditching the current racing beat bar (54107) and 14mm rear bar setup. Increasing spring rate helped greatly and I feel it wants more but I would like to get a bigger bar on the front that has some greater tuning options. Freeing up the suspension normally demands more spring rate as well so without going crazy I'll just make a couple changes at a time to see what it wants.
Engine wise this setup is proving very reliable and for reference we double dip this car in TT and ST all weekend so it see's 10-16 sessions per event which is fairly demanding. Now power wise were gonna need a little more if were going to compete with the tractor like power bands of the BMW's that have won nationals the past couple years but we have to keep reliability as the top concern. A turbo is the easy button but with as much run time as we demand I just don't feel that will be the wisest choice for us, if it was just me running ST or TT I would slap that on and be done. So choosing the correct top end parts, compression and electronic throttle control I feel we can create the power band we need to compete. For reference the BMW's make 235hp from 5k to 8k which is going to be what I want to replicate, not so much the 235hp but somewhere in between that and 200hp. Should be fun I think.
One problem I'm not sure how to eliminate is the tire's rotating on the rims, and its all four. I thought about just balancing the wheel and accepting what vibration it creates but would like to figure out an actual fix for it as in my mind its kind of like a slipping clutch and were losing time. I've read a huge variety of ideas from dry mounting, hairspray, knurling or media blasting the beads but thought maybe I'm missing the magic bullet someplace. If not I guess I'll throw all the ideas together and see if it sticks
I'll post up a short vid later and some more pics!
Were you able to fix the vibration issues? Could it be the engine itself? I'm following a couple of these builds and it seems they both mention something about unusual vibrations at speed. I think the other mentioned deleting the balance shafts as well.
02-14-2019, 07:50 PM
NASA ST4 build - LE5 Ecotec power
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