saltfish Posted November 30, 2008 Report Share Posted November 30, 2008 So I'm moving this from the bs forum. Basically I have a rebuilt motor with a 274 cam, bs eliminated, njv marnel head, 2.25 aluminum hard pipes, 4" intercooler, upgraded fuel/oil pumps, 3" exhaust, apexi safc-II, 1g mas, and the GT28RS disco potato attached with a custom t3 log manifold. So you'd think I'd be making decent power at least decent torque but no...it sucks. After talking with some people I may think that the disco potato is too small for our motors. I don't see how it makes 300whp on a 1.8l and not even 200 on my motor. I checked everything with a wideband and I don't know if there are any other issues. Compresson seems fine and I think my injectors are fine but really don't know. Below is from 13.5lbs on the gt28rs - I'm thinking that I'm just going to switch to a t3/t4, at least I know people have done that. So far I havent found anybody else who did a gt28rs on our cars. I want to stay tbi and care more about stoplight tq numbers than high hp...now I have neither http://img171.imageshack.us/img171/1699/dynour6.jpg Link to comment Share on other sites More sharing options...
86TSiGuy Posted November 30, 2008 Report Share Posted November 30, 2008 So I'm moving this from the bs forum. Basically I have a rebuilt motor with a 274 cam, bs eliminated, njv marnel head, 2.25 aluminum hard pipes, 4" intercooler, upgraded fuel/oil pumps, 3" exhaust, apexi safc-II, 1g mas, and the GT28RS disco potato attached with a custom t3 log manifold. So you'd think I'd be making decent power at least decent torque but no...it sucks. After talking with some people I may think that the disco potato is too small for our motors. I don't see how it makes 300whp on a 1.8l and not even 200 on my motor. I checked everything with a wideband and I don't know if there are any other issues. Compresson seems fine and I think my injectors are fine but really don't know. Below is from 13.5lbs on the gt28rs - I'm thinking that I'm just going to switch to a t3/t4, at least I know people have done that. So far I havent found anybody else who did a gt28rs on our cars. I want to stay tbi and care more about stoplight tq numbers than high hp...now I have neither http://img171.imageshack.us/img171/1699/dynour6.jpg Yeah something is wrong or the 28rs sucks hardcore. I've never seen any info on that turbo on a G54B, but you should be making 200lb/ft at 10.5psi on the stock 12a with those upgrades. How does it run? Link to comment Share on other sites More sharing options...
Dcrasta Posted December 1, 2008 Report Share Posted December 1, 2008 http://www.phantasmusa.com/gt2860rs.html According to this information, this turbo either has a AR. 64 or AR .84 If you have the Ar .64 you have too small a turbine section (like i told you on the fone). I think that is the problem. Maybe you can order a different turbine and exhaust housing that way you wont have to change up all of your setup. Link to comment Share on other sites More sharing options...
Maxzillian Posted December 1, 2008 Report Share Posted December 1, 2008 Do you have a flow map for this turbo charger? It may be possible that the G54B isn't a good match for that turbo. Link to comment Share on other sites More sharing options...
saltfish Posted December 1, 2008 Author Report Share Posted December 1, 2008 GT28RS flow map well there is one...mine is a .64 I may be able to order a new housing and turbine but for that price I think I'm better off just going to a t3/t4 and selling the potato. I have noticed that when I'm at stoplights sometimes the idle will almost dip to stalling out point and then "burp" itself back up. Not sure if I have a leaking injector but I thought that might show up in the egt/wideband. Link to comment Share on other sites More sharing options...
Dcrasta Posted December 1, 2008 Report Share Posted December 1, 2008 GT28RS flow map well there is one...mine is a .64 I may be able to order a new housing and turbine but for that price I think I'm better off just going to a t3/t4 and selling the potato. I have noticed that when I'm at stoplights sometimes the idle will almost dip to stalling out point and then "burp" itself back up. Not sure if I have a leaking injector but I thought that might show up in the egt/wideband. That sounds like a vacuum leak. I would check all the hoses (if you haven't replaced them I would replace all the vacuum lines). Also check the intercooler lines / Intake hoses between the MAS and Throttlebody. Link to comment Share on other sites More sharing options...
JustPaus_88TSi Posted December 1, 2008 Report Share Posted December 1, 2008 What do we know about the turbo. 0.64 A/R and it flows 35lbs/min(from a map I found) which is 500CFM, or about as much as a 16g. A TD05 housing is roughly 0.48A/R. What has a TD05-12a turbo made before at 15psi? 215hp/278tq(UltimateLurker) So this disco potato flows 180CFM more than a 12a, AND has a larger A/R, yet it makes less power? I don't think so. It's not a "poorly matched" turbo, as it's a couple steps above the stocker. It should spool quick, which keeps the TQ numbers up. That dyno doesn't show that at all. Something is up with your engine, something is "off". Link to comment Share on other sites More sharing options...
Dcrasta Posted December 1, 2008 Report Share Posted December 1, 2008 Thanks for the #s JP, I think us local guys need to have a meet (or monthly) I seem to have a few guys nearby maybe we can meet at DiscoPotato's house Link to comment Share on other sites More sharing options...
Maxzillian Posted December 2, 2008 Report Share Posted December 2, 2008 Yeah, judging by the maps I'd say that turbo is a pretty good match. Looks to be a good turbo for high boost and peak efficient flow matches pretty closely to a 18G, but the efficiency does drop off sooner and comes in line with the 16G. I agree, look elsewhere for the problem. Link to comment Share on other sites More sharing options...
saltfish Posted December 2, 2008 Author Report Share Posted December 2, 2008 Yeah well hopefully this weekend we can do a thorough test for vacuum leaks. That would great if it was just that simple. I will let everybody know. Are there other diagnostics that you guys reccomend? Link to comment Share on other sites More sharing options...
saltfish Posted December 2, 2008 Author Report Share Posted December 2, 2008 Just thought of something else...I noticed now that the hvac system doesn't seem to blow in the upper vents and not at all in the vents closet to the doors. This is vaccum controlled right? Also when I bought it the previous owner told me that sometimes a metal tube that goes to the auto tranny comes loose and could affect the overdrive. Could this also be a vacuum leak? Link to comment Share on other sites More sharing options...
Hoosierquest Posted December 2, 2008 Report Share Posted December 2, 2008 The vacuume line for the HVAC runs along the fire wall then up the passenger fender and attaches to a vacuume pump up behind the header panel. I think it also connects to the lower portion of the intake. There is also a boost reference line that runs to the tranny. I belive it locks the converter as boost builds, I could be way off on that as I have not really dug into my Auto car yet. The service manual may help you track down those vacuume lines. www.starquestgarage.com Link to comment Share on other sites More sharing options...
mstieg Posted December 2, 2008 Report Share Posted December 2, 2008 repost and bump this thread back once your other probs. are solved and you're able to give the potato a decent shot. I'm curious what it'll do on the G54B, almost as much as my own turbo. Good luck Link to comment Share on other sites More sharing options...
jinx Posted December 2, 2008 Report Share Posted December 2, 2008 disco close in size to a 16g. You mounted a T2 flanged turbo on a T3 manifold ? Maybe your bottleneck(turbulence) is where manifold meets turbo ? did u run another turbo immediately before the 28 ? If it performed weak, the problem could be cam or ignition timing Link to comment Share on other sites More sharing options...
Maxzillian Posted December 4, 2008 Report Share Posted December 4, 2008 Just thought of something else...I noticed now that the hvac system doesn't seem to blow in the upper vents and not at all in the vents closet to the doors. This is vaccum controlled right? Also when I bought it the previous owner told me that sometimes a metal tube that goes to the auto tranny comes loose and could affect the overdrive. Could this also be a vacuum leak? Nope, the system only controls air going to all face vents, not selective. The only way to shut off the face vents is to switch them to blow using outside air pressure using the levers on the vents. Link to comment Share on other sites More sharing options...
Dcrasta Posted December 5, 2008 Report Share Posted December 5, 2008 I took a look at the car yesterday. 1: The timing (Cam) looks late by a tooth to me. (couldnt correct this as I didnt have tools (and neither did Adam!LOL)).. I will be bringing my expert second opinion with me saturday (my brother the Tech). 2: Distributor may need to be R&R . We will verify the movement of the mechanical advance. 3: I will help remove the EGR and block off the port for Adam as he has a 'option' when It comes to emissions and he has waaaay too many vacuum lines under that hood (and too many things t'ed together). Any brainstorming please post it up cause we want to fix the Disco Potato and launch the DC/MD/VA Starion/Conquest club . Link to comment Share on other sites More sharing options...
87chrycon Posted December 5, 2008 Report Share Posted December 5, 2008 Do the EGR delete/blockoff and remove as many vacuum lines as you can as Dcrasta suggests. Then do the purge cannister delete as well if you are able to get away with this in your area. I have had no ill effects from this easy removal. One area that many people neglect when checking the vac. lines is the vac. pump (for HVAC) area behind the front header panel. There is a small plastic reducer there that connects the pump line to the vac. line that runs from the passenger side fender. This (passenger side line) is almost always split at that reducer. If you release the radiator overflow tank from its wedge position (pull up on it til it pops out) it will make it a bit easier to get to the reducer if you have large hands. Replacing that whole line for a couple dollars is money well spent. If you replace it using the old one and a plastic vac. connector to pull the other one through the holes in the frame makes it quick. Another one that is almost always hard and brittle is the one that feeds the HVAC system from the stand alone port on the intake man. under the row of three on the throttle body-- again use a plastic connector and the old line to feed the new line through the maze. All vac. hoses at the little T's and L's are also suspect for vacuum leaks as any 20+ year old car that is turbo ( hot under hood temps) will easily harden the rubber lines where they expand over these little fittings. I replaced every vacuum line in the engine bay and did the 2 deletes above in an afternoon so it is not that time consuming and they will last years. Link to comment Share on other sites More sharing options...
Dcrasta Posted December 6, 2008 Report Share Posted December 6, 2008 Welp, I will let Adam fill you guys in but the cam was a tooth late. Had to bring in the big guns (Brother) to get er done. we knocked it out in under an hour (outside in the cold makes you work fast) .. We also fixed the ignition timing (put a light on it and set it to 10bdc) and a problem with the turbo coolant line (line busted we resolved that). So hopefully we can get some real numbers. Likely the motor was assembled late and no one has had a chance to really drive it with the correct timing . Next will be egr delete.. Link to comment Share on other sites More sharing options...
saltfish Posted December 6, 2008 Author Report Share Posted December 6, 2008 Yes big thanks to DcRasta and family...this will probably get a ton of business (wanted or unwanted ) in the mod atlantic region. So anyways the low end power is vastly improved and the idle sounds like a new car (turns out loping v8 sound was not desired ) For those that we were wondering it seems that the previous owner had the 274 put it in the new build and they must have always had it a tooth off. Now my mission is to get a wideband on this and redo the SAFC-II. I have the halmeter a/f meter and for what thats worth its showing that its running rich. Might be bogged down a bit from the old tune. Even so its much much more responsive. Also noticed that the Potato is heating my wires to an uncomfortable warmth and now I need a garrett heat shield if anybody knows where there is one. Link to comment Share on other sites More sharing options...
Technology Posted December 6, 2008 Report Share Posted December 6, 2008 You can make your own heat shield with basic hand tools like pliers and a drill. I cut up my old stock one and used it to protect the brakeline on the passender inner fender. Works amazing. Also, I'd take that narrow back gauge and throw it in the garbage. I would never ever, evereverever, use a narrow band again. outside of about 14.3-14.9AFR it's completely inaccurate. Widebands for the win, plus there are places haveing awesome sales on them such as www.maperformance.com Good luck tuning! keep 'er around 12.5 Link to comment Share on other sites More sharing options...
mstieg Posted December 6, 2008 Report Share Posted December 6, 2008 Also, I'd take that narrow back gauge and throw it in the garbage. Man, I plan on selling mine off on ebay to at least recoupe a few dollars. Link to comment Share on other sites More sharing options...
Dcrasta Posted December 7, 2008 Report Share Posted December 7, 2008 Cheapest on on ebay. YOu could make something like this with some creative sheetmetal TurboHeatShield Link to comment Share on other sites More sharing options...
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